# Why So Many Large Mammals In Africa? **URL:** \ **Category:** Factual Questions\ **Created:** [October 11, 2006, 11:21am UTC](https://boards.straightdope.com/t/why-so-many-large-mammals-in-africa/376037 "2006-10-11T11:21:55Z")\ **Posts on this page:** 20\ **Page:** 3
**Author:** ![NoCoolUserName](https://avatars.discourse-cdn.com/v4/letter/n/5fc32e/32.png) [@NoCoolUserName](https://boards.straightdope.com/u/NoCoolUserName)\ **Post date:** [October 13, 2006, 12:52am UTC](https://boards.straightdope.com/t/why-so-many-large-mammals-in-africa/376037/41 "2006-10-13T00:52:49Z")
[QUOTE=John Mace] And lest we forget, the OP is asking about Africa. It was propose, up thread, that because we (_H. sapiens_) evolved in Africa that the African megafauna evolved with us, and thus adapted to our hunitng skills. That’s a seductive argument, but I’m wondering if that is what biologists think. For one thing, our speices adopted newer hunting techniques quite rapidly, and much of that evolution was cultural/technological rather than biological. If you go back 100k years, you find anatomically modern humans in Africa (and a few in Israel), but they weren’t using tools that were appreciably more sophisticated than what the Neanderthals were using in Europe. It’s not until ~60k years ago that you start seeing an explosion of technical advances in the tool kit like the common use of bone and more finely crafted points as well as jewelry and other indications of artistic expression (indicating a cognitive development putting “them” on par with “us”). Recent findings of possible shell beads dating from ~ 75k years ago may push that date back further, but not by all that much. [/QUOTE] But that doesn’t make the thesis false. Elephants in particular are fairly intelligent. They may have developed behaviors that saved them from extinction (and passed them on in a herd-like way) over the period of time that humans developed better weapons and hunting techniques. It’s a WAG, but seems like a reasonable one. The larger beasts on other continents would not have had the same amount of time to adjust their habits. On another front, those folks quoted WAY upthread who have developed (one assumes computer) models of how many people it would take to hunt megafauna to extinction–where did they get their numbers? It seems unlikely that they have observed very many megafauna who are unaccustomed to humans. I’m not denigrating their work, just saying we might need several grains of salt here. ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [October 13, 2006, 5:02am UTC](https://boards.straightdope.com/t/why-so-many-large-mammals-in-africa/376037/42 "2006-10-13T05:02:12Z")
[QUOTE=NoCoolUserName] But that doesn’t make the thesis false. Elephants in particular are fairly intelligent. They may have developed behaviors that saved them from extinction (and passed them on in a herd-like way) over the period of time that humans developed better weapons and hunting techniques. It’s a WAG, but seems like a reasonable one. The larger beasts on other continents would not have had the same amount of time to adjust their habits. [/QUOTE] Don’t get me wrong-- I agree that it seems like a reasonable assumption. I’m just wondering what the data tell us. Is there any evidence that the African megafauna today is biologically different from the megafauna of 50k years ago. Maybe that’s too difficult a question to answer, but I’d like to hear from the experts. ---
**Author:** ![GIGObuster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gigobuster/32/421_2.png) [@GIGObuster](https://boards.straightdope.com/u/GIGObuster)\ **Post date:** [October 13, 2006, 6:44am UTC](https://boards.straightdope.com/t/why-so-many-large-mammals-in-africa/376037/43 "2006-10-13T06:44:09Z")
[QUOTE=John Mace] Don’t get me wrong-- I agree that it seems like a reasonable assumption. I’m just wondering what the data tell us. Is there any evidence that the African megafauna today is biologically different from the megafauna of 50k years ago. Maybe that’s too difficult a question to answer, but I’d like to hear from the experts. [/QUOTE] It seems experts are divided if it was climate, disease or humans what caused the extinction of the mega fauna, the real answer is likely a combination of all those factors. [http://www.bbc.co.uk/nature/programmes/tv/monsterswemet/experts\_europe.shtml](http://www.bbc.co.uk/nature/programmes/tv/monsterswemet/experts_europe.shtml) However, all those factors do IMO involve humans on the move (changing climate allowing and/or forcing humans to move, and humans also carrying diseases to other continents) [http://www.dbc.uci.edu/~sustain/bio65/lec04/b65lec04.htm](http://www.dbc.uci.edu/~sustain/bio65/lec04/b65lec04.htm) > [@](#): > > LATE PLEISTOCENE EXTINCTIONS > > In late Pleistocene, during the last 50,000 years, there were mass extinction events in many different parts of the world, involving at least 200 genera (plural of genus = a group of related species). But this was different from previous episodes of mass extinction: > > 1. It was much more selective, involving mainly the megafauna: the large herbivores (mammoths, mastodons, huge ground sloths, cave bears, woolly rhinoceros, other rhinoceroses, etc.) and the carnivores that fed on them, the dire wolves and saber-tooth cats. There was no accelerated extinction of smaller terrestrial species, plants, or marine organisms. > > The following disappeared from America, Europe and Australia: > > All herbivores… \> 1000 kg > > 75% of herbivores… 100-1000 kg > > 41% of herbivores… 5-100 kg > > \< 2% of herbivores… \< 5kg > > 1. It occurred at different times on different land masses: > > Time of start of > major extinction episodes > (years before present) > > Africa and S.E. Asia… 50,000 > > Australia…50,000 > > North Eurasia…13,000 > > North America…11,000 > > South America…10,000 > > West Indies…4,000 > > New Zealand…900 > > Madagascar…800 > > This excludes any global catastrophe or climatic change as an explanation. > > In all of these cases except Africa, the extinctions occurred shortly after the first arrival of prehistoric humans. The first humans were faced with animals that had evolved in the absence of human predators, and the animals were probably easily overcome. Therefore, the most plausible explanation is that these extinctions were caused by overexploitation by human hunters. > > In Africa, massive extinction does not coincide with the arrival of humans. Humans had been evolving there for millions of years without causing mass extinctions (they may not have been as carnivorous as their descendants in other parts of the world) but it does coincide with the maximum development of advanced early Stone Age hunting cultures. > > Many authors have remarked that to see what the Pleistocene was like, you should go to Africa. Africa still has more large herbivores (including elephants, hippos, rhinos, etc.) than any other place on earth. **But, even in Africa, the big game we see today is only about 70% of the genera that were present in mid-Pleistocene. About 50 genera disappeared about 40,000 years ago.** Even then, when a new convenient idea appeared, it was quickly adopted by all humans that got hold of it. I have the feeling humans developed new techniques on how to hunt big prey and not even (many) African animals were fast enough to adapt to the new human schemes. ---
**Author:** ![DrDeth](https://avatars.discourse-cdn.com/v4/letter/d/b487fb/32.png) [@DrDeth](https://boards.straightdope.com/u/DrDeth)\ **Post date:** [October 13, 2006, 3:11pm UTC](https://boards.straightdope.com/t/why-so-many-large-mammals-in-africa/376037/44 "2006-10-13T15:11:47Z")
[QUOTE=GIGObuster] It seems experts are divided if it was climate, disease or humans what caused the extinction of the mega fauna, the real answer is likely a combination of all those factors. However, all those factors do IMO involve humans on the move (changing climate allowing and/or forcing humans to move, and humans also carrying diseases to other continents) . [/QUOTE] Good points. I will point out that when humans were able to move, so were other critters- of course, sometimes along with the humans. Your second cite contains a small error: \*"The following disappeared from America, Europe and Australia: All herbivores… \> 1000 kg"\* Bison (including the Wisent) can & do weigh upwards of 1000kg- The biggest (American) specimens on record have weighed as much as 1140 kg, per Wiki. Note from your second cite is also a quote about Martin "Detailed study of late Pleistocene extinctions in North America (Martin, 1986) suggests that they happened over just a few hundred years. This explains why there is so little archaeological evidence for hunting of mammoths in the New World. … Paul Martin has suggested that the human population quickly expanded south from the Bering land bridge, and exterminated the big game as they went (“Blitzkrieg” model). Martin, P. S.1986. ". **John** , I equated Blitzkrieg with Aquatic Ape as they were both very interesting hypothesis, both based entirely on several interesting and amazing coincidences, and neither had any empirical data to back them up. Martin even admited his hypothesis couldn’t be falsifable, which measn it couldn’t be tested. Later, it turns out he was wrong, and there were tests and his original theory \*was \* false. From your link, it appears he later modified his original radical hypothesis. Still, he is unable to test his hypothesis. The “mostly climate” side has some interesting facts and arguments too, from the second page of John’s cite:"\*Guthrie (1984, 1995) suggests that the type of climatic change at the end of the Pleistocene was unparalled during the Quaternary and altered plant community mosaics resulting in a general trend of extinctions and dwarfing during the early Holocene. … Vegetation communities during the Pleistocene are described by Guthrie (1984) as mosaics of high plant diversity that supported a high diversity of “climatically incompatible” animals forming “disharmonious mixtures”. Pleistocene age deposits show (now) northern species, such as grouse (Canachitas canadensis) and lemming (Synoptomys cooperi) existing with (now) southern species such as muskrat (Neofiber alleni) and skunk (Conepatus leuconotus) in Georgia (Guthrie, 1984). Guthrie (1984) argues that the diversity found during the Pleistocene was a result of the long growing season that led to a “sympatric tolerance” between plants that fostered diversity rather than homogeneity. This environment favored animals that were habitat generalists, that needed to supplement their diets with a variety of different plants to obtain necessary nutrition and avoid eating too many plants with strong anti-herbivory compounds. ``` The climate during the Pleistocene was colder and drier (Hoffecker, et. al., 1993; Guthrie, 1995), which favored the growth of grasses, forbes, and sages, which Guthrie describes as the "mammoth steppe". This grassy steppe environment was productive as an abundant source of nutrition for the herbivorous large-bodied mammoths, supported by the analysis of the Shandrin frozen mammoth's stomach content, found in Siberia in 1972 (Lister and Bahn, 1994). In his article, Guthrie attibutes the highly nutritious flora to the "plant-hostile" climate of this epoch, of colder winters with reduced snow cover and cooler, windier summers. This environment created an energetic stress on plants that led to their investment of energy into fiber-carbohydrate growth, rather than into anti-herbivory defenses. Guthrie (1984) suggests that the Holocene interglacial led to a decline in mosaic vegetation and an increase in "zoned" or homogeneous vegetation communities, which resulted in a decreased quality and quantity of resources for mammals and thus a shorter growing season. These restrictions caused a lowering of the high faunal diversity, large body size, and large distributional ranges that characterized the Pleistocene. This type of environment during the last interglacial favored a mammals that are habitat specialists that eat a homogenous, monocultural diet (Guthrie, 1984). Thus, the large bodied mammals that dominated the Pleistocene, were subject to a decrease in quantity and quality in food supply, and increasing seasonality at the end of the Pleistocene, that led to the extinction of some mammals and created a biotically different Holocene environment. "* ``` There is a huge debate going on over whether it was _mostly_ human (deterministic) or _mostly_ climatic (stochastic). Since humans arrived, there has been a considerable increase in extinctions, but nearly all have both factors. For example, take the Great Auk (the _original \* Pen-guin_). There is no doubt that the last few Great Auks were killed by dudes working for collectors/“naturalists” and museums in 1844, on the island of Eldey, near Iceland. \*(deterministic) \* The last few were hunted down as they had become very rare. But what made them so rare? Well, they were hunted by man since at least 2000BC, so that’s deterministic. But _generally_, when a certain prey gets hard to find, food hunters \*usually \* stop going after it, picking on something easier (if you are hunting to survive, you go after the easiest calories). Which more or less happened, as the Great Auk had been resticted to a hard to get to island off Iceland, and the hunting was more or less down to a few birds being collected for “naturalists” :rolleyes: . Then comes the stochastic factor- in 1830, the island of Geirfuglasker (the Auk’s home) blew up and sunk, taking just about the last auks with it. This led to their great rarity, which led to the last few being hunted down. Mostly deterministic, sure, but the last home and breeding ground being sunk suddenly by volcanic action is certainly a critical stochastic factor. Anyway, I am not taking sides in the “great debate”. But, I can say that Martin’s original radical hypothesis has been proven wrong. Almost no expert now says it is entirely one or the other. So simplistic answers like\*:“Clovis man, with the Spear, in a century”\* 😛 are part of the past, with Piltdown Man. - you can win a bar bet with this factiod, it is generally conceded that the word “penguin” was originally a name for the Auk or _Geirfugl_. ---
**Author:** ![NoCoolUserName](https://avatars.discourse-cdn.com/v4/letter/n/5fc32e/32.png) [@NoCoolUserName](https://boards.straightdope.com/u/NoCoolUserName)\ **Post date:** [October 13, 2006, 4:17pm UTC](https://boards.straightdope.com/t/why-so-many-large-mammals-in-africa/376037/45 "2006-10-13T16:17:53Z")
[QUOTE=John Mace] Don’t get me wrong-- I agree that it seems like a reasonable assumption. I’m just wondering what the data tell us. Is there any evidence that the African megafauna today is biologically different from the megafauna of 50k years ago. Maybe that’s too difficult a question to answer, but I’d like to hear from the experts. [/QUOTE] I was trying (not too successfully, it seems) to make the point that it might not be biological change at all. Many of the African megafauna didn’t make it–maybe they were the ones without the intelligence and/or ability to pass learning along (herd behavior). Mama elephant sees curious baby elephant move towards the funny upright apes. Baby elephant gets smacked and learns to watch out for said apes. Mama does that because HER mama did it. Giant sloths didn’t have the same capability, perhaps. Note that I’m speaking ex-cathedra from my bellybutton here. I have no background in this stuff. I’m a software geek. ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [October 14, 2006, 1:24am UTC](https://boards.straightdope.com/t/why-so-many-large-mammals-in-africa/376037/46 "2006-10-14T01:24:15Z")
[QUOTE=DrDeth] After all, humans have been around in asia for millions of years too, and as the OP pointed out- few large mammals. [/quote] Quite simply untrue. Up until the start of the Iron Age Asia had _more large species than Africa._. In fact IIRC Asia had more large species than Africa up until the 16th century. > [@](#): > > Next, N. America had billions of Bison, and the natives had hardly put a dent in the population. Simply untrue. The three endemic American bison species became extinct around 10, 00o years ago; surely that qualifies as “putting a dent in the population”? The sole remaining bison species in the Americas is the newly arrived Eurasian bison, a species that co-evolved with modern humans. > [@](#): > > Youd think that if humans had hunted the giant sloth and the mastodon to extinction, they’d have gone for the easier to kill and more useful bison first. Can we please have a reference that mastodons and giant sloths are harder to kill? > [@](#): > > Next- hunting rarely drives any species to extinction (hunting drives species to \*near \* extinction, instead). I’ll just repeat what I said in an earlier thread: I fail to see any practical distinction between “humans precipitated the extinctions with the timing and extent dictated by climate” and “humans caused the extinction”. I’ve really never understood those who try to adopt such a position as though somehow mitigating the role of humans. > [@](#): > > Go ahead- name a few large, successful mammalian species that humans have driven to extinction by hunting in the last few hundred years- after modern firearms made killing so much easier. Large _AND_ successful? What you are asking for is a list of large species that proved they could successfully deal with human predators but somehow couldn’t cope with firearms. I have to question exactly what such a list is supposed to tell us. > [@](#): > > Here’s an abstract of an article about Australian megafauna extinction: Yes, and an article that has been thoroughly debunked by Flannery, amongst others. Quite simply the article relies on three highly flawed assumption. The first is that humans only prey on either small or large species but never the both together. In fact what we find is that humans prey on large species, and when they become scarce they turn to small game. That allows human populations densities to remain high and never allows large game species to recover. Thus the conclusion that “smaller megafauna would have been more readily exterminated than larger megafauna because they would have been harvested at a higher rate to satisfy the demand for meat” is fatally flawed, a sis the extended argument that regula fauna would have suffered before megafuna. The second flaw is the contention that “hunting efficiencies required to drive medium (500 kg) and larger (1000 kg) sized megafauna to extinction appear unrealistically high”. When humans interact with naïve animal populations hunting efficiencies are indeed unrealistically high. Naïve animals simply allow humans to walk up and club them on the head. The third flaw is that the megafauna existed in eucalypt savannas, whereas Bowman’s own research has shown that the current Eucalypt savannas of Northern Australia are almost entirely anthropogenic. Bowman has taken a lot of flak for overlooking something that he his own prior research did so much to establish. > [@](#): > > In other words, actual scientific results show that the “overkill hypothesis” is wrong. No, it does not. What those tow articles show is that there are certain assumptions required which are debatable. Nonetheless the majority of scientists accept the overkill hypothesis. Even Bowman himself accepts the overkill hypothesis to a limited extent, albeit combined with fire mediated vegetation change. > [@](#): > > Three things led to the megafauna extinction: Climate change (the same climate change that allowed humans to spread)… Can you please explain what climate change allowed humans to spread to Australia, New Zealand, Madagascar and New Caledonia to name but a few points? > [@](#): > > ….. new species (of which humans were one, sure, but many other species came along- including our friend the rat).. Sigh. I debunked this nonsense when you brought it up in previous thread. Instead of conceding the point there you trot it out again now. There were no exotic rats in Australia when the megafauna vanished. There were no exotic animals at all except humans. > [@](#): > > … and new diseases spread by those new species (which I guess you can consider another form of “new species”). Can you provide any evidence at all that a disease has ever lead to the extinction of a megafaunal species? > [@](#): > > Overkill/Blitzkrieg (being a single source reason for the extinctions) is **wrong** , according to my sources, _and_ according to Colibri, if I read his posts correctly. 1. You seem to be labouring under the misapprehension that overkill and blitkreieg are synonyms. They are not. 2. Neither blitzkrieg nor overkill are wrong according to your sources. According to your sources they require assumptions which not everyone agrees with. If you wish to debate those assumptions then I will happily enlighten you over in GD. [QUOTE=DrDeth] In fact, IMHO our “little freind” 😛 _Rattus sp_ has caused more actual extinctions that us humans with puny spears clutched in our opposable thumbed hands. Of course, when H.Sapiens introduces _Rattus_, the forthcoming extinctions can be laid at our feet. [/quote] Yes, you state din an earlier thread that there were no endomic Rattus species in Australia. When I debunked that claim and pointed out there were dozens you refused to even reply. Yet here you are repeating the same basic claim. [QUOTE=DrDeth] the Overkill/Blitzkreig hypothesis _is_ on a line with the Aquatic Ape hypothesis- it’s an _extremist_ idea with few expert backers and less facts. [/quote] Nonsense. Overkill is supported by such luminaries as Jared Diamond, Mike Archer and Tim Flannery amongst others. Far from having few backers it is accepted by the majority of biologists and palaeontolgists. Blitzkreig can still boast the support of Flannery and Diamond amongst many others. As far as facts, they fall very heavily in the Overkill camp. The disputants rely rather upon models. > [@](#): > > \*\*Colibri \*\* seems to weigh in that Human intervention being more important that climate, but depending on the local and period, if I read him correctly. No, Colibri and I agree on this one: humans were responsible. Animal populations were decimated or forced into refugia due to human activity and as a result were unable to weather environmental change. Had humans not intervened the species would have ridden out the climate change just as they had numerous times in the past. Your position is akin to claiming that humans didn’t exterminate the dusky seaside sparrow. That species was killed by a grassfire. The fact that human shad reduced the population to 3 breeding females was irrelevant because a grassfire finally did for them and grassfires were natural in their environment. This is clearly nonsense. The fire was natural but the species condition was anthropogenic and it was the anthropogenic factors that left them vulnerable. So it was for climate change induced extinction: the coup de grace may have been natural but extinction was entirely attributable to humans. > [@](#): > > Blitzkrieg [is] based entirely on several interesting and amazing coincidences, and [has no] empirical data to back [it] up. Simply untrue. There is a large amount of empirical data to back up the blitzkrieg hypothesis. Datings of human arrivals, weights and habitats of extinct species, survival on islands or other human isolated refugia. These are all empirical evidence of blitzkrieg. The only way you could possibly say that there is no empirical evidence if you wish to argue that no past event can be said to be supported by empirical evidence. [QUOTE=NoCoolUserName] I was trying (not too successfully, it seems) to make the point that it might not be biological change at all. Many of the African megafauna didn’t make it–maybe they were the ones without the intelligence and/or ability to pass learning along (herd behavior). Mama elephant sees curious baby elephant move towards the funny upright apes. Baby elephant gets smacked and learns to watch out for said apes. Mama does that because HER mama did it. Giant sloths didn’t have the same capability, perhaps. [/QUOTE] Highly unlikley Almost every species over 30kg was exterminated in Australia, yet koalas and wombats survived. These are species that are noted for being as dumb as fungus. Similarly in North America the intelligent elephants and horses were exterminated while the bison survived. In South America the giant ‘gorilla’ monkeys were exterminated while the less intelligent camelids and rattites survived. There isn’t any correlation between survival and intelligence, learning ability or even maternal care. More likely these species simply had no genetic defence against humans and had no ability to evolve such a defence. Large slow breeding species such as elephants and giant monkeys never got operated on by the processes that selected for more skittish individuals in other species. ---
**Author:** ![DrDeth](https://avatars.discourse-cdn.com/v4/letter/d/b487fb/32.png) [@DrDeth](https://boards.straightdope.com/u/DrDeth)\ **Post date:** [October 14, 2006, 6:26am UTC](https://boards.straightdope.com/t/why-so-many-large-mammals-in-africa/376037/47 "2006-10-14T06:26:11Z")
Well, sorry **Blake** , I am leaving on vacation. Next time,come in earlier,willya? Err, dude “There were no exotic rats in Australia when the megafauna vanished. There were no exotic animals at all except humans.”- you do know about the dingo? You also know that Australia is just one single continent right? The fact that Rattus has driven scads of species into extinction doesn’t means it has done so every where. We are talking about the whole world, not just one area. Did ya even read my cites? Can you dispute them? Do you have any cites of your own or just your own opinion? :rolleyes: Anyway, thanks **Scissorjack** for a great OP, thanks **John Mace** for the debate, thanks everyone for your contributions,and have fun n your vacation, **Colibri.** I’ll be back sometimes between Tuesday and Thursday. Enjoy! ---
**Author:** ![Scissorjack](https://avatars.discourse-cdn.com/v4/letter/s/c67d28/32.png) [@Scissorjack](https://boards.straightdope.com/u/Scissorjack)\ **Post date:** [October 14, 2006, 10:56am UTC](https://boards.straightdope.com/t/why-so-many-large-mammals-in-africa/376037/48 "2006-10-14T10:56:56Z")
[QUOTE=DrDeth] Anyway, thanks **Scissorjack** for a great OP… [/QUOTE] Oh, I’m liking this one: I know when I’m out of my depth, but this one is an education in itself, and many thanks to all who’ve contributed. **Blake** , I was hoping you’d show up - I always learn from what you have to contribute. ---
**Author:** ![mr.jp](https://avatars.discourse-cdn.com/v4/letter/m/48db29/32.png) [@mr.jp](https://boards.straightdope.com/u/mr.jp)\ **Post date:** [October 14, 2006, 5:57pm UTC](https://boards.straightdope.com/t/why-so-many-large-mammals-in-africa/376037/49 "2006-10-14T17:57:51Z")
How did humans actually kill these large animals, such as mammoths? Did they trap them with fire, and throw spears at them? > [@](#): > > giant skunks Hehe, that sounds bad. ---
**Author:** ![yBeayf](https://avatars.discourse-cdn.com/v4/letter/y/e274bd/32.png) [@yBeayf](https://boards.straightdope.com/u/yBeayf)\ **Post date:** [October 14, 2006, 6:49pm UTC](https://boards.straightdope.com/t/why-so-many-large-mammals-in-africa/376037/50 "2006-10-14T18:49:33Z")
> [@](#): > > How did humans actually kill these large animals, such as mammoths? Did they trap them with fire, and throw spears at them? Yes and yes. Another popular method was to drive entire herds off of cliffs. [Article](http://www.pnas.org/cgi/content/full/95/24/14576) on prehistoric hunting strategies. ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [October 20, 2006, 9:25pm UTC](https://boards.straightdope.com/t/why-so-many-large-mammals-in-africa/376037/51 "2006-10-20T21:25:54Z")
[QUOTE=DrDeth] Well, sorry **Blake** , I am leaving on vacation. Next time,come in earlier,willya? [/quote] Well I notice we are both back now so we can contnue. > [@](#): > > Err, dude “There were no exotic rats in Australia when the megafauna vanished. There were no exotic animals at all except humans.”- you do know about the dingo? Sigh. The dingo arrived in Australia no more recently than 5, 000 YBP. The last of the megafauna vanished no later than 25, 000 YBP. I repeat: your claims that there were any exotic animals in Australia when the megafauna vanished is pure bunkum. I have debunked it comprehensivley for you in previous threads which I will link to if you wish. Your claim has no basis in fact. > [@](#): > > The fact that Rattus has driven scads of species into extinction doesn’t means it has done so every where. We are talking about the whole world, not just one area. Precisely. And this sort of selective application is what makes attribution of the extinctions to non-anthropogenic or indirect anthropogenic causes so weak and such shoddy science. According to your position it is exotic animals, except in cases such as Australia where there were no exotics, and then it has to be disease, except in cases such as North Am where disease is implausible, and then it has to be fire, except in cases such as NZ where fire wasn’t used in most regions and so on and so forth on an ad hoc, case-by-case basis for every major landmass. This approach requires a selctive application of the facts to fit your theory. It makes for a weak argument and incredibly shoddy science. In contrast attributing the extinctions to direct, deliberate anthropogenic forces requires only a single assumption to be made that can be applied and tested universally. > [@](#): > > Did ya even read my cites? Can you dispute them? Umm, dude, I just provided several hundred words critiquing your “cites”. Not sure how you missed that. > [@](#): > > Do you have any cites of your own or just your own opinion? “Cites” for what exactly? As you would well know form past experience you only need to ask and I provide any refernces you like, but you will need to ask for something specific. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [October 20, 2006, 11:39pm UTC](https://boards.straightdope.com/t/why-so-many-large-mammals-in-africa/376037/52 "2006-10-20T23:39:46Z")
[QUOTE=DrDeth] So again, here are my cites: [http://www.blackwell-synergy.com/doi/abs/10.1046/j.1466-822X.1998.00285.x?journalCode=geb](http://www.blackwell-synergy.com/doi/abs/10.1046/j.1466-822X.1998.00285.x?journalCode=geb) _Do you think Drs. DAVID CHOQUENOT & D. M. J. S. BOWMAN are wrong, and what cites do you have to support your opinion?_ [/quote] That’s merely an application of mathematical predator-prey models to the Australian case. As such, it is heavily dependent on its basic assumptions, and it can hardly be considered to be any kind of definitive “proof” that humans were not responsible for the extinction. In any case, **Blake** has already addressed reasons why the assumptions may be wrong and the analysis incorrect. [QUOTE=DrDeth] [http://www.pnas.org/cgi/content/abstract/99/23/14624](http://www.pnas.org/cgi/content/abstract/99/23/14624) I]Do you think Drs. Barry W. Brook, and David M. J. S. Bowman are wrong, and what cites do you have to support your opinion?\* [/QUOTE] Again, this is a modelling excercise. In this case, it is used to question other analyses that purport to show that the overkill hypothesis is correct. They conclude their abstract: > [@](#): > > Contrary to recent claims, the existing data do not prove the “blitzkrieg” model of overkill. Note that all they are claiming is that the “blitzkrieg” model _is not proved;_ this is quite far from establishing that it is incorrect. Once again, IMO mathematical models, while they can be instructive, cannot be considered to be definitive proof on either side of the question, because it is impossible to be sure about the reliability of the underlying assumptions. [QUOTE=DrDeth] [http://www.sciencemag.org/cgi/content/abstract/306/5693/70](http://www.sciencemag.org/cgi/content/abstract/306/5693/70) _Do you think Drs. Anthony D. Barnosky, Paul L. Koch, Robert S. Feranec, Scott L. Wing, & Alan B. Shabel are wrong, and what cites do you have to support your opinion?_ [/QUOTE] As I said before, I consider this to be an excellent summary of the evidence to date. However, you continue to misinterpret it as somehow supporting your position. I am not sure if you have actually read it yourself, or only seen the abstract and the bits I have quoted previously. It generally affirms, as I have said, that human impacts were almost certainly the most important factor in some regions, exclusive of climate; and in other areas human impacts interacted with climate to produce more severe megafaunal extinctions than would have otherwise taken place. In only very limited regions or cases, if any, does the article suggest that climate may have been the most critical factor. From the article, which unfortunately is not available on line: > [@](#): > > How far has the debate about Pleistocene extinction on continents progressed in the last 40 years? The case for humans contributing to extinction is now much stronger than it was in the early days, with support from recent work on chronology, simulations, paleoclimatology, paleontology, and archaeology. Yet it is an oversimplification to say that an abrupt wave of hunting-induced extinctions swept continents right after first human contact. Instead, the evidence shows that blitzkrieg sensu stricto can be firmly rejected in western Europe, Siberia, Alaska, and probably Australia and central North America. Note that rejection of “blitzkrieg sensu strictu” does not mean rejection of the conclusion that humans instead of climate caused the extinctions. The blitzkrieg hypothesis is a narrow and extreme one, postulating that the extinctions occurred almost simultaneously with the arrival of modern humans. Instead, extinctions could have been more drawn out - the “sitzkrieg hypothesis” as described well by **John Mace** and due both to hunting and other human impacts. > [@](#): > > Without late Pleistocene climatic change, it is likely that species such as horses in Alaska and mammoths and giant Irish deer in central Eurasia would have survived longer, despite the presence of humans. The recent information now points toward humans precipitating the extinction, but also to an instrumental role for late Pleistocene climatic change in controlling its timing, geographic details, and perhaps magnitude. The mechanism for climatic effects is likely to be found in detailed species-by-species analyses (19), rather than in one of the three existing global ecological models (10, 59, 60), none of which is fully consistent with observations. > > Data density and quality are still uneven. The Eurasian record is increasingly good and reveals that late Pleistocene climatic change contributed to extinction by driving range adjustments in large mammals. An idea that needs further testing is that the arrival and population expansion of Homo sapiens sapiens began to fragment megafaunal ranges by 30,000 years ago, ultimately restricting megafauna to inviable populations in far northern refugia by the end of the Pleistocene. It doesn’t say that horses, mammoths, and Irish deer would have survived, merely that they would have survived _longer_ in the absence of climate change - but humans were still ultimately responsible for their demise. As I have said before, I agree with **Blake** that there is little difference in saying that “humans precipitated the extinction” and “humans caused the extinction.” > [@](#): > > Australian evidence suggests that megafaunal extinction followed human arrival, and that both probably preceded significant global or regional South Pacific climatic change, which is consistent with a role for humans. However, the timing of key events still cannot be bracketed within error bars less than 10,000 years, the youngest records of extinct megafauna are controversial, and local environmental changes may differ from the global or regional pattern (4, 5). In other words, the arrival of humans and not climate was probably the most important factor in Australia (even if blitzkrieg sensu strictu is incorrect), but details remain to be worked out. > [@](#): > > In South America, published data on extinction chronology is accumulating but awaits critical analysis. In Africa, better temporal resolution is needed to assess how the timing of the few extinctions matches local environmental changes and human impacts. For South America and Africa data are less clear; however, human effects, particularly in South America, could certainly have been important. > [@](#): > > In contrast, robust dating verifies simultaneous climatic change and first human contact in the conterminous United States, where extinctions were particularly rapid and pronounced. Support for human impacts includes (i) indisputable hunting of two extinct species, (ii) clustering of extinctions within 1,500 years (and perhaps less) of first contact with Clovis hunters, (iii) widespread distribution of Clovis hunters, (iv) simulations, and (v) more pronounced extinction than in mid-Pleistocene glacial-interglacial transitions. On a broader North American scale, the demise of megafaunal species without significant human presence in Alaska is consistent with some role for climate. So it would seem that Barnosky et al. support the Clovis/blitzkrieg hypothesis. I personally don’t think it is correct, but I will expand on this in another post. > [@](#): > > [http://www.unl.edu/rhames/courses/current/requiem-overkill.pdf](http://www.unl.edu/rhames/courses/current/requiem-overkill.pdf) > _Do you think Drs. Grayson & Meltzer are wrong, and what cites do you have to support your opinion?_ > > Note that this last cite comes with 93 footnotes! As I have said, I personally agree that Martin’s Clovis-blitzkrieg hypothesis is not correct. However, it is wrong to contend, as **DrDeth** does, that just because this one extreme scenario is wrong, that humans were not responsible for megafaunal extinctions. **DrDeth** seems to confuse the specific blitzkrieg hypothesis of Martin with the more general proposition that humans were responsible for the extinctions. However, I do not think that that particular article is very good; it is mostly just an anti-Martin diatribe. [QUOTE=DrDeth] And while I am in awe of **Colibri** , [/QUOTE] Glad to hear it. 🙂 > [@](#): > > somehow I doubt even he will say that "Drs. DAVID CHOQUENOT, D. M. J. S. BOWMAN, Barry W. Brook, Anthony D. Barnosky, Paul L. Koch, Robert S. Feranec, Scott L. Wing, Alan B. Shabel, Grayson & Meltzer " are all wrong and he is right. But he doesn’t say so, he more or less agrees with them. The difference is in degree, and there what we have is- from the experts- “Alternatively, climate change in the late Pleistocene may have played an important role in the extinction of Australian megafauna”, "Contrary to recent claims, the existing data do not prove the “blitzkrieg” model of overkill. " and "Firmer chronologies, more realistic ecological models, and regional paleoecological insights still are needed to understand details of the worldwide extinction pattern and the population dynamics of the species involved. " “Wrong” is not the correct word to use with regard to the first two citations; they merely do not prove anything definitively one way or the other. The second two citations I agree with. However, the first, according to my reading, indicates that human impacts were in general more significant than climate change; while the second contradicts only one narrow hypothesis, not the more general impact of humans. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [October 21, 2006, 12:27am UTC](https://boards.straightdope.com/t/why-so-many-large-mammals-in-africa/376037/53 "2006-10-21T00:27:35Z")
[QUOTE=DrDeth] Next- hunting rarely drives any species to extinction (hunting drives species to \*near \* extinction, instead). [/quote] This statement is nonsense. > [@](#): > > Go ahead- name a few large, successful mammalian species that humans have driven to extinction by hunting in the last few hundred years- after modern firearms made killing so much easier. We’ve had this discussion before, and you continually narrow and redefine your terms in order to have fewer species it can apply to. The last time you brought it up, it concerned any “widespread, successful species,” not just mammalian. When I brought up Passenger Pigeons and Great Auk, you claimed that habitat destruction being partly involved in the case of the former, and a volcanic eruption in the case of the latter, somehow negated the fact that overhunting was overwhelmingly the major factor in the demise of these widespread, extremely successful species. Now you want to limit the case to mammals, and only look at cases where humans have caused complete extinction of an entire species; ignoring the fact that humans have unequivocally caused extinctions over large parts of species’ ranges, that survival of some formerly widespread species, such as the bison, has been entirely due to human intervention; and that other species that became extinct, such as Steller’s Sea Cow, were not “widespread and successful” in recent times only because of former human hunting. > [@](#): > > Steller’s Sea Cow was a distinct species. But there was maybe around 1000 of them alive when Steller found them (and ate them ). It wasn’t “successful” (at that point in time anyway) and likely Steller just hastened the extinction by a few decades. Sad story though. Steller’s Sea Cow originally had a very wide distribution around the North Pacific rim and was highly successful. The reason for its extinction on mainland coasts was certainly aboriginal hunting; it clearly can’t be attributed to climate change because some survived in the Commander Islands until the 1700s. Since a population had evidently persisted in these uninhabited islands for many thousands of years, there is no reason to suppose they would have become extinct there without human hunting. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [October 21, 2006, 12:31am UTC](https://boards.straightdope.com/t/why-so-many-large-mammals-in-africa/376037/54 "2006-10-21T00:31:08Z")
[QUOTE=Colibri] **DrDeth** seems to confuse the specific blitzkrieg hypothesis of Martin with the more general proposition that humans were responsible for the extinctions. [/QUOTE] On re-reading this thread, I withdraw this remark. **DrDeth** does understand the difference. But he keeps bringing up evidence against the Martin blitzkrieg hypothesis as if this also refuted the significance of human impacts in general. ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [October 21, 2006, 1:40am UTC](https://boards.straightdope.com/t/why-so-many-large-mammals-in-africa/376037/55 "2006-10-21T01:40:13Z")
[QUOTE=Colibri] So it would seem that Barnosky et al. support the Clovis/blitzkrieg hypothesis. I personally don’t think it is correct, but I will expand on this in another post. [/quote] Please do, I’d like to hear your views on this. > [@](#): > > On re-reading this thread, I withdraw this remark. DrDeth does understand the difference. But he keeps bringing up evidence against the Martin blitzkrieg hypothesis as if this also refuted the significance of human impacts in general. I’m not certain he does appreciate the difference. This is because he continually uses phrases such as > [@](#): > > Overkill/Blitzkrieg (being a single source reason for the extinctions) is wrong, according to my sources… That seems to clearly imply that he sess Overkill and Blitzkrieg as synonymous. I would appreciate it at this stage if Dr. Deth would clarify that he does appreiate the distinction and doe sunderstand that even if one is wrong the other need not be. > [@Colibri](#): > > We’ve had this discussion before, and you continually narrow and redefine your terms in order to have fewer species it can apply to. The last time you brought it up, it concerned any “widespread, successful species,” not just mammalian. This time it isn’t just mammalian, it is large _and_ mammalian, _and_ successful _and_ began to decline since 1500. As I noted earlier, I have trouble seeing what such a list could possibly tell us. It would at best be a list of species that could cope perfectly well with modern human hunting but for some reason succumbed to firearms and not to the plethora of other weapons in the human arsenal. What exactly could that tell us WRT the topic at hand? ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [October 21, 2006, 3:50am UTC](https://boards.straightdope.com/t/why-so-many-large-mammals-in-africa/376037/56 "2006-10-21T03:50:12Z")
[QUOTE=Blake] Please do, I’d like to hear your views on this. [/quote] I gave a pretty thorough critique of the Clovis evidence in [this post](http://boards.straightdope.com/sdmb/showpost.php?p=7332151&postcount=43) in the thread that **John Mace** linked to in post 7 of this thread. To sum up, in the original Martin blitzkrieg hypothesis, he postulated that the Clovis big-game hunting culture colonized North America from Asia, entering as soon as the ice sheets had melted enough to allow a passage east of the Rockies through the Canadian Great Plains, and that Clovis represented the first humans in the Americas. Martin proposed that these big-game hunters, with superabundant prey, built up a high but transient population density along the colonization front. This high-density population is what caused the rapid extinctions; most local extinctions, according to Martin, may have taken place within a few decades or at most centuries. As the colonization front spread through the Americas, the megafauna became extinct in its wake. However, there is little (or no) evidence for this specific scenario. Some of the evidence against it: 1. There is now strong evidence that humans were in the Americas well before Clovis, by at least several thousand years, although evidently at quite low densities. 2. There is no clear evidence that Clovis came from Asia. 3. Although Clovis spread rapidly through North and Central America, there is no clear evidence that the spread was from north to south. 4. There were also post-Pleistocene big-game hunting cultures in South America, and Martin and others have postulated that these descended from Clovis. However, there is no good evidence that this is so, and these cultures are more likely to have been of independent origin from populations already present in South America. There evidently was a convergent development of big-game hunting cultures, which used similar but not exactly equivalent tool kits, at the end of the Pleistocene in both continents. While I do not think that the specific Clovis-blitzkrieg scenario is true, I do think that humans were mostly responsible for the megafaunal extinctions in the Americas. This may have been due to either attrition over several thousand years - sitzkrieg - or may have been due to the origin and spread of big-game hunting cultures in both North and South America post-Pleistocene - a modified, non-directional, blitzkrieg. I note that Grayson and Meltzer, cited by **DrDeth** above, argue against Martin by saying that 1) humans were present in North America before Clovis; and 2) some of the megafaunal extinctions were pre-Clovis. This is exactly what one would expect if sitzkrieg were responsible for these extinctions. However, I have not reviewed the evidence closely enough to know whether the extinctions were really spread out over time, or as clustered as Martin claims. Barnosky et al evidently do accept that the extinctions were clustered, and Clovis was responsible for most of them. Although the megafaunal extinctions in the Americas may have coincided with both the spread of big-game hunting cultures, and with a period of rapid climate change, I would argue the first was paramount because the extinctions affected all climatic zones and all habitats, even those that were expanding. Proboscidians became extinct from the tundra to the eastern forests to southwestern semi-arid areas to the tropical forests of Central and South America. Likewise all ground sloths became extinct, whether they lived in deciduous forest, sagebrush desert, savannas, or tropical forests. Likewise for the other groups of the megafauna. It’s hard to postulate a climatic change that would have done all of them in simultaneously, especially when most of the smaller species survived quite well. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [October 21, 2006, 3:42pm UTC](https://boards.straightdope.com/t/why-so-many-large-mammals-in-africa/376037/57 "2006-10-21T15:42:05Z")
[QUOTE=DrDeth] Three things led to the megafauna extinction: Climate change (the same climate change that allowed humans to spread), [/quote] As has already been stated, humans spread into most areas long before major climate change occurred, in particular Australia. In orher regions, climate change may have had an effect on the extent and timing of human impacts, but the presence of humans was crucial (in most areas). > [@](#): > > new species (of which humans were one, sure, but many other species came along- including our friend the rat), As \*\*Blake \*\* has already stated, rats had exactly zero to do with megafaunal extinctions anywhere, whether on continents or islands. Human-introduced rats have had major impacts on smaller fauna on islands, but probably had little effect on larger species such as moas in New Zealand, and certainly had zero effect on giant lemur or elephant extinctions in Madagascar. I don’t recall that anyone has ever proposed that rats had anything to do with the extinction of mammoths or giant ground sloths. What other species did you have in mind whose spread would have caused megafaunal extinctions? > [@](#): > > and new diseases spread by those new species (which I guess you can consider another form of “new species”). Of all the hypotheses advanced to explain the megafaunal extinctions, I think disease is by far the weakest one, as a general explanation on a global scale. Certainly disease has had an impact in isolated areas in historical times, but only within restricted groups (e.g. avian malaria in the Hawaiian Islands, but this has affected mainly one order, the passerines). Only Australia was isolated enough that it might be imagined that novel diseases from the outside would have had much of an impact. However, the extinctions affected not only mammals there but also large reptiles and birds. The mammals were marsupials of a wide variety of orders. It is extremely unlikely that humans, which were the only species to colonize Australia prior to the megafaunal extinctions, could have transported pathogens that would have affected all these groups. For Eurasia and the Americas the hypothesis doesn’t hold water either. Extensive interchange of faunas took place through Beringia during previous interglacials without provoking extensive extinctions. Again, the extinctions affected a wide variety of unrelated groups, from proboscidians to ungulates to carnivores to edentates to large rodents. It is impossible to imagine that one or a few diseases transferred through faunal interchange could have been responsible for extinctions across such a wide range of taxa. In any case, this hypothesis, like so many others, does not explain which smaller animals were much less affected by extinctions. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [October 21, 2006, 5:26pm UTC](https://boards.straightdope.com/t/why-so-many-large-mammals-in-africa/376037/58 "2006-10-21T17:26:21Z")
[QUOTE=Colibri] elephant extinctions in Madagascar. [/QUOTE] Make that Elephant **Bird** extinctions in Madagascar. ---
**Author:** ![DrDeth](https://avatars.discourse-cdn.com/v4/letter/d/b487fb/32.png) [@DrDeth](https://boards.straightdope.com/u/DrDeth)\ **Post date:** [October 21, 2006, 6:40pm UTC](https://boards.straightdope.com/t/why-so-many-large-mammals-in-africa/376037/59 "2006-10-21T18:40:14Z")
I do not and did not claim that humans were not a cause. In fact,they might well have been the Primary cause. What I claim is that human _hunting_ was not the\* only \*cause as \*\*robby \*\*seem to claim in post #3, and as the \*original \*Martin Hypothesis claimed. Climate played a more or less important role,and humans had plenty of ways to induce extinction other than by just hunting. **Blake** used Jared Diamond is his “appeal to authority” but Diamond in “Guns Germs & Steel” carefully considered both sides- “overkill” and climate. His conclusion was “Hence it seems to me most likely that the giants were indeed exterminated by humans, both directly (by being killed for food) and indirectly (as the result of fires and habitat modifications caused by humans). But regardless of whether the “overkill” or climate hypothesis proves correct…” ---
**Author:** ![DrDeth](https://avatars.discourse-cdn.com/v4/letter/d/b487fb/32.png) [@DrDeth](https://boards.straightdope.com/u/DrDeth)\ **Post date:** [October 21, 2006, 6:56pm UTC](https://boards.straightdope.com/t/why-so-many-large-mammals-in-africa/376037/60 "2006-10-21T18:56:29Z")
[QUOTE=Colibri] Quote: Originally Posted by DrDeth Next- hunting rarely drives any species to extinction (hunting drives species to near extinction, instead). This statement is nonsense. . [/QUOTE] I would have thought so myself, except I had been reading David Quammen’s “The Song of the Dodo” (an excellent book). Pg 542 of my edition, contains the following " Mark Shaffer’s contribution to the Blue Book was titled _“Minimum Viable Populations: Coping with Uncertainty”_…Although systematic pressures inflicted by wilful human activity can drive a species down to the margin of viability, Shaffer wrote, the terminal event- extinction- will generally involve an element of chance." (By “chance” he is talking about Stochastic factors here,not Deterministic factors. ) pp 516 “In general, there are four sources of uncertainty that a population may be subject”, Shaffer wrote. He listed them: demographic stochasticity, environmental stochasticity, natural catastrophes, genetic stochasticity." In other words, human hunting generally drives a species to near-extinction “margin of viability”, and stochastic factors finish them off. Sure recently, as in the case of the Mauritius Kestrel,humans can _re_-intervene and save the species. [Previous page](https://boards.straightdope.com/t/why-so-many-large-mammals-in-africa/376037.md?page=2) [Next page](https://boards.straightdope.com/t/why-so-many-large-mammals-in-africa/376037.md?page=4)