# If there were no"Toba catastrophe," would more than one human species be alive today? **URL:** \ **Category:** Great Debates\ **Created:** [March 27, 2005, 11:39pm UTC](https://boards.straightdope.com/t/if-there-were-no-toba-catastrophe-would-more-than-one-human-species-be-alive-today/296512 "2005-03-27T23:39:24Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![BrainGlutton](https://avatars.discourse-cdn.com/v4/letter/b/82dd89/32.png) [@BrainGlutton](https://boards.straightdope.com/u/BrainGlutton)\ **Post date:** [March 27, 2005, 11:39pm UTC](https://boards.straightdope.com/t/if-there-were-no-toba-catastrophe-would-more-than-one-human-species-be-alive-today/296512/1 "2005-03-27T23:39:24Z")
It’s a curious fact that _Homo sapiens,_ despite a global distribution of population and a wide variation in physical appearance, has less genetic diversity than chimpanzees. The currently prevailing theory to explain this is the “Toba catastrophe” – [http://en.wikipedia.org/wiki/Toba\_catastrophe\_theory:](http://en.wikipedia.org/wiki/Toba_catastrophe_theory:) > [@](#): > > Within the last three to five million years, after human and ape lineages diverged from the hominid stem-line, the human line produced a variety of human species. According to the Toba catastrophe theory, a massive volcanic eruption changed the course of human history by severely reducing the human population (called a ‘bottleneck’). Around 75,000 years ago the Toba caldera in Indonesia erupted with a force three thousand times more powerful than Mount St. Helens. > > According to Ambrose, this led to a decrease in the average global temperatures by as much as 15°C. This massive environmental change is believed to have created population bottlenecks in the various human species that existed at the time; this in turn accelerated differentiation of the isolated human populations, eventually leading to the end of all the other human species except for the branch that became modern humans (see volcanic winter). > > Some geological evidence and computed models support the plausibility of the Toba catastrophe theory, and genetic evidence suggests that all humans alive today, despite their apparent variety, are descended from a very small population (see mitochondrial Eve). Using the average rates of genetic mutation, some geneticists have estimated that this population lived at a time coinciding with the Toba event. > > According to this theory, after Toba, and when the climate and other factors permitted, humans once again fanned out from Africa migrating first to Indochina and Australia, and later to the Fertile Crescent and the Middle East. Migration routes to Asia created population centers in Uzbekistan, Afghanistan, and India. Divergences in skin color appeared, due to varied melanin levels, which were adaptations to the varying UV intensities around the world. Europe became populated by migrants from the Uzbekistan region when the last ice age ended and Europe began to be more hospitable. Suppose it had never happened? Science knows of at least twelve species in the genus _Homo_ other than _Homo sapiens._[http://en.wikipedia.org/wiki/Human\_evolution](http://en.wikipedia.org/wiki/Human_evolution) (N.B.: Not all of these were still extant at the time of the Toba catastrophe, and at least two – _Homo neanderthalensis_ and _Home floresiensis_ lived on for several millennia afterwards.) If there had never been a Toba catastrophe, would we have had to share this world with other “human” races? Or would we eventually have wiped them all out? (Or is it possible one of them would have wiped **us** out?) Or would we have made slaves of the intellectually inferior species? (Harry Turtledove explored that theme in the alternate-history novel _A Different Flesh,_ in which the Europeans discover a New World inhabited not by Indians but by _Homo erectus._) Also, what would be the long-term effects of a wider, pre-Toba range of genetic diversity within _Homo sapiens_ itself? ---
**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:** [March 28, 2005, 4:00am UTC](https://boards.straightdope.com/t/if-there-were-no-toba-catastrophe-would-more-than-one-human-species-be-alive-today/296512/2 "2005-03-28T04:00:04Z")
Unlikely. There isn’t any evidence that the “Toba catastrophe” had anything to do with the extinctions of the Neanderthals, and they aren’t around any more. I doubt that our “less enlightened” ancestors would have allowed a seperate species of \*Homo \*to survive. Unless that species was extremely isolated somewhere, they’d be toast. ---
**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:** [March 28, 2005, 4:23am UTC](https://boards.straightdope.com/t/if-there-were-no-toba-catastrophe-would-more-than-one-human-species-be-alive-today/296512/3 "2005-03-28T04:23:59Z")
> [@BrainGlutton](#): > > _Homo neanderthalensis_ and _Home floresiensis_ lived on for several millennia afterwards.) _Homo erectus_ too, which may have survived up to 27,000 years ago on Java. _H. neanderthalis_ survived to at least 30,000 years ago, and\* H. floresiensis\* to 18,000 years ago. So at least four species of \*Homo \* survived at least 45,000 years _after_ the Toba event. It doesn’t sound likely that it was responsible for the extinction of three of them. More likely it was \*H. sapiens \* that did the others in. ---
**Author:** ![XT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/xt/32/456_2.png) [@XT](https://boards.straightdope.com/u/XT)\ **Post date:** [March 28, 2005, 4:26am UTC](https://boards.straightdope.com/t/if-there-were-no-toba-catastrophe-would-more-than-one-human-species-be-alive-today/296512/4 "2005-03-28T04:26:52Z")
Didn’t the australopithecines die out long before 75,000 years ago? By that time I thought pretty much there was only one genus of hominid left (neanderthals afaik being simply a subspecies or a cold weather adapted version). I could be totally wrong about both of these, as its been over a decade since my college anthropology classes…and they were only electives anyway. 🙂 -XT ---
**Author:** ![BrainGlutton](https://avatars.discourse-cdn.com/v4/letter/b/82dd89/32.png) [@BrainGlutton](https://boards.straightdope.com/u/BrainGlutton)\ **Post date:** [March 28, 2005, 5:54am UTC](https://boards.straightdope.com/t/if-there-were-no-toba-catastrophe-would-more-than-one-human-species-be-alive-today/296512/5 "2005-03-28T05:54:01Z")
> [@xtisme](#): > > Didn’t the australopithecines die out long before 75,000 years ago? By that time I thought pretty much there was only one genus of hominid left (neanderthals afaik being simply a subspecies or a cold weather adapted version). I could be totally wrong about both of these, as its been over a decade since my college anthropology classes…and they were only electives anyway. 🙂 > > -XT According to the Wikipedia article on “Human evolution” (linked in the OP), and pages linked from it: The _Australopithecus_ genus of hominids first appeared roughly 3.9 million years ago and was extinct long before the Toba catastrophe. _A. africanus_ once was thought ancestral to the _Homo_ genus, but hominid fossils apparently belonging to genus _Homo_ have been discovered which predate _A. africanus._ The split might have been with _A. afarensis._ The first human (defining human as any member of genus _Homo_) species was _H. habilis,_ which lived from 2.4 to 1.5 MYA. _H. egaster_ lived from about 1.8 to about 1.25 MYA. _H. rudolfensis_ is a proposed species that might or might not be distinct from _habilis._ _H. georgicus,_ known from fossils discovered in Georgia (in the Caucasus) and dated to 1.8 MYA, might transitional between _habilis_ and _erectus._ _H. erectus_ lived from about 1.25 MYA to 70,000 years ago. _H. heidelbergensis_ (common ancestor of both _H. neanderthalensis_ and _H. sapiens_) lived from about 500,000 years ago to about 300 TYA. _H. sapiens idaltu_ is a subspecies of _H. sapiens_ that lived over 160 TYA in Africa. _H. floresiensis_ (the “hobbit”) survived until at least 12,000 years ago. Six skeletons of an extinct species, _H. antecessor,_ were discovered in Spain in 1994. _H. neanderthalensis_ (classed as a separate species, not a subspecies of _H. sapiens,_ but that question remains controversial) lived from about 250 to 30 TYA. Our species, _H. sapiens,_ appeared 200 TYA. > [@](#): > > Between 400,000 years ago and the second interglacial period in the Middle Pleistocene, around 250,000 years ago, the trend in cranial expansion and the elaboration of stone tool technologies developed, providing evidence for a transition from H. erectus to H. sapiens. The direct evidence suggests that there was a migration of H. erectus out of Africa, then a further speciation of H. sapiens from H. erectus in Africa. (There is little evidence that this speciation occurred elsewhere.) Then a subsequent migration within and out of Africa eventually replaced the earlier dispersed H. erectus. However, the current evidence doesn’t preclude multiregional speciation, either. This is a hotly debated area in paleoanthropology. “Sapiens” means “wise” or “intelligent.” The article also mentions _H. cepranensis_ and _H. rhodesiensis_ but no information is provided. Based on timeline alone, _erectus_ and possibly _sapiens idaltu_ might have been wiped out by the Toba catastrophe – or perhaps they were merely displaced/marginalized/exterminated by the _H. sapiens_ diaspora from Africa, as _neanderthalensis_ almost certainly was. On the other hand, it seems to be the Toba catastrophe that is responsible for the narrow range of genetic diversity within _H. sapiens._ And there might well have been other human species living at the time of the Toba catastrophe, and wiped out by it, that have not yet been discovered. The existence of _H. floresiensis,_ after all, was not even suspected until a few months ago. ---
**Author:** ![Evil\_Captor](https://avatars.discourse-cdn.com/v4/letter/e/f17d59/32.png) [@Evil\_Captor](https://boards.straightdope.com/u/Evil_Captor)\ **Post date:** [March 28, 2005, 3:45pm UTC](https://boards.straightdope.com/t/if-there-were-no-toba-catastrophe-would-more-than-one-human-species-be-alive-today/296512/6 "2005-03-28T15:45:39Z")
Yeah, but wasn’t floriensis discovered on an isolated island, thus making it more or less moot? Also, given that the island floriensis was discovered on was in Indonesia, presumably much nearer to the Toba eruption than African or European humanoids, wouldn’t it have been mujch more likely to be wiped out by Toba than other species? I guess what I am saying is that floriensis is probably a moot point in the argument, re: Toba. But it does lead me to wonder if the floriensis pop. isn’t a remnant population of a species that once had much wider geographical dispersal, whose remains were discovered precisely because they were relatively recent. ---
**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:** [March 28, 2005, 4:23pm UTC](https://boards.straightdope.com/t/if-there-were-no-toba-catastrophe-would-more-than-one-human-species-be-alive-today/296512/7 "2005-03-28T16:23:37Z")
**BG** : You have to be careful when reading something like Wikipedia about a subject like human sepciation. There are many “species” floating around in the literature that aren’t widley accepted. Species designations keep changing, and new are added almost ever time a new fossil is discovered. You get a lot more press and recognition when you announce “New species of hominind discovered” as opposed to “New fossil of existing species discovered”. It wasn’t that long ago that Neanderthals were considered a subspecies of Sapiens, but most anthropologists now recognize it as a distinct species. Even still, the designation of an extinct population as a separate species is always going to be somewhat arbitrary. _Homo floresiensis_, for example, has been PROPOSED, but still has lots of question marks associated with it. The fossils have not been widely circulated for other scientists to study and until that happens, there is always going to be an “\*” by its species designation. If you believe every proposed species is real, it would appear that the human line speciated every 100k years or so. That’s just not realisitic. If you look at other extant large mammals with lifespans on the order of humans, you’d be hard pressed to find two different species in the same genus that didn’t branch off from each other at least a million years ago. And even then, those “species” are likely to be cross fertile even if mating in the wild is rare. A good example of this is the [red wolf](http://en.wikipedia.org/wiki/Red_wolf). Scientists are in disagreement if this wolf is truely a distinct species or just a population of grey wolf/coyote hybrids. In this case, the species designation takes on a political aspect, since that determines whether or not the population can be considered “endangered”. ---
**Author:** ![chappachula](https://avatars.discourse-cdn.com/v4/letter/c/d2c977/32.png) [@chappachula](https://boards.straightdope.com/u/chappachula)\ **Post date:** [March 28, 2005, 6:43pm UTC](https://boards.straightdope.com/t/if-there-were-no-toba-catastrophe-would-more-than-one-human-species-be-alive-today/296512/8 "2005-03-28T18:43:42Z")
> [@Colibri](#): > > More likely it was H. sapiens that did the others in. I know that most experts agree, but I have never fully understood this. It’s easy to see why H. sapiens could kill off the primitive Neanderthals if they were competing for the same food and shelter. But why did they have to compete? Neanderthals had technology and physiology that enabled them to survive the ice age and hunt woolly mammoths–they could have run away from the new homo sapiens spreading thru Africa, and migrated to the colder climates. The planet is one huge place for cave men who didn’t have broadband access. It seems like there should have been room for the smaller brained, but physically stronger Neanderthals to live separately from H. Sapiens. (And if Neanderthal had survived, we probably would have kept 'em as slaves.Sure would make for an interesting comparison with whatever alien creatures we may one day encounter…) ---
**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:** [March 28, 2005, 7:13pm UTC](https://boards.straightdope.com/t/if-there-were-no-toba-catastrophe-would-more-than-one-human-species-be-alive-today/296512/9 "2005-03-28T19:13:07Z")
> [@chappachula](#): > > I know that most experts agree, but I have never fully understood this. I wouldn’t say “most experts agree.” Like most things about early humans, the idea that _H. sapiens_ might have done in the other species of _Homo_ it encountered is pretty much speculation. But that speculation is based largely on what happened when different groups of _sapiens_ of differing cultural levels have encountered one another. The more primitive group was as often as not wiped out, or at the very least subjugated. And this probably happened not just recently, but tens of thousands of years ago as well. > [@](#): > > It’s easy to see why H. sapiens could kill off the primitive Neanderthals if they were competing for the same food and shelter. But why did they have to compete? Neanderthals had technology and physiology that enabled them to survive the ice age and hunt woolly mammoths–they could have run away from the new homo sapiens spreading thru Africa, and migrated to the colder climates. The planet is one huge place for cave men who didn’t have broadband access. Of course they were often competing for the same food and shelter. Early _sapiens_ hunted big game and lived in caves, just as Neanderthals seem to have done. And I don’t know how _neanderthalensis_ could have “'run away.” _Sapiens_ was perfectly capable of living anyplace that _neanderthalensis_ could. > [@](#): > > It seems like there should have been room for the smaller brained, but physically stronger Neanderthals to live separately from H. Sapiens. For the record, \*neanderthalensis \* had a _larger_ brain than the average _sapiens_, although it was somewhat differently shaped. And just because there might be “enough room” wouldn’t necessarily prevent conflict from occurring. Certainly there was “enough room” in Tierra del Fuego and in Tasmania for primitive groups to survive there in company with Europeans, but those groups were pretty much eradicated anyway. ---
**Author:** ![BrainGlutton](https://avatars.discourse-cdn.com/v4/letter/b/82dd89/32.png) [@BrainGlutton](https://boards.straightdope.com/u/BrainGlutton)\ **Post date:** [March 28, 2005, 11:09pm UTC](https://boards.straightdope.com/t/if-there-were-no-toba-catastrophe-would-more-than-one-human-species-be-alive-today/296512/10 "2005-03-28T23:09:20Z")
> [@Colibri](#): > > Early _sapiens_ hunted big game and lived in caves, just as Neanderthals seem to have done. Nitpick: We call prehistoric humans “cavemen” because a lot of their remains have been found in caves – but that’s because caves naturally preserve bones, artifacts and wall paintings. A lot of them probably lived in tents or huts (it’s not exactly a major technological challenge to build one – the pre-Columbian American Indians, whose technology was purely stone-age, had their teepees and wigwams), but the elements gradually destroyed all trace of them. ---
**Author:** ![BrainGlutton](https://avatars.discourse-cdn.com/v4/letter/b/82dd89/32.png) [@BrainGlutton](https://boards.straightdope.com/u/BrainGlutton)\ **Post date:** [March 28, 2005, 11:12pm UTC](https://boards.straightdope.com/t/if-there-were-no-toba-catastrophe-would-more-than-one-human-species-be-alive-today/296512/11 "2005-03-28T23:12:30Z")
> [@John Mace](#): > > **BG** : You have to be careful when reading something like Wikipedia about a subject like human sepciation. I know, I know . . . but the Wiki article was more plain and readable than anything else I could find on the same subject. Do you know of any site that makes clear exactly how many known human species were living 75,000 years ago? ---
**Author:** ![BrainGlutton](https://avatars.discourse-cdn.com/v4/letter/b/82dd89/32.png) [@BrainGlutton](https://boards.straightdope.com/u/BrainGlutton)\ **Post date:** [March 28, 2005, 11:18pm UTC](https://boards.straightdope.com/t/if-there-were-no-toba-catastrophe-would-more-than-one-human-species-be-alive-today/296512/12 "2005-03-28T23:18:46Z")
> [@John Mace](#): > > _Homo floresiensis_, for example, has been PROPOSED, but still has lots of question marks associated with it. The fossils have not been widely circulated for other scientists to study and until that happens, there is always going to be an “\*” by its species designation. Not sure I follow you . . . there’s no question the fossils exist, is there? Or do you mean they still might decide to classify the “hobbits” as a subspecies of _H. sapiens?_ Hard to see that, if their braincases were really that small. ---
**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:** [March 28, 2005, 11:37pm UTC](https://boards.straightdope.com/t/if-there-were-no-toba-catastrophe-would-more-than-one-human-species-be-alive-today/296512/13 "2005-03-28T23:37:07Z")
**BG** : At 75k years ago, there probably is concensus on Sapiens, Neanderthal and Asian Erectus. Floresiensis is still too new to be broadly accepted, but for the sake of argument we can probably say that some different species existed on the Flores Island. It’s the earlier species that I question. For instance, do we really need a _H. antecesor_ given that we have _erectus_, _ergaster_, _rudolfensis_, and _heidelbergensis_? As for _floresiensis_: there is no doubt that the fossils exist. But they are being held in Indonesia (can’t remember the name of the Indonesian scientist in charge) and not being made available for study. Yes, the discovering crew has claimed they are a new species, but not enough other scientists have looked at the actual fossils and until that happens, it’s unclear how the chips will eventually fall. The case looks pretty strong for a new species, but it’s still too early to say definitively.