Animals of the New World

What theories have been postulated regarding the size of animals in the New World versus those in the Old? Other than bears, moose and bison, the New World is void of any truely large mammals and even the ones we do have don’t match up to their comparisons in the Old (i.e. mountian lions and jaguars don’t really equal lions and leopards). Certainly, nothing on par with the tigers, elephants, giraffes and other African and Asian beasts. From what I understand, North America used to be home of some of the largest of Earth’s creatures including the tyrannosaur, brachiosaur, giant sloth, various ‘saber toothed’ cats and other prehistoric giants but now the best we can come up with is the grizzly and polar bears and it all goes downhill from there. Reasons?


“I guess one person can make a difference, although most of the time they probably shouldn’t.”

No theory here, but aren’t bisons the biggest ruminant in the cow genre?

Could it have something to do with the climate?
It wasn’t cold in North America when the dinosaurs ran amock.
Africa is very warmer than North America, so is India- places where elephants live.
And think of plants-
the trees in Massachusetts have smaller leaves than those of the Southern-native catalpa tree.
Tobacco leaves are large, banana leaves are large- all from warm climates.
Insects in the tropics are sometimes as wide around as your hand- and they aren’t found in the cooler climates of the states.
And the earth as a whole was much warmer in the Mezozoic Era when the dinosaurs lived.
I know that there are exceptions like the polar bear, but I see a relation here between size and climate.

I remember Jared Diamond talking about the destruction of the megafauna in the New World. According to him, this happened around 12,000 BCE.

His theory was that this is strong evidence for the “recent” argument in the When Did People First Get Here debate.
He was saying that most of the megafauna, not having evolved along with humans, didn’t have the right defenses to survive the human onslaught.
Other examples of this(of his): Australia and Madagascar.

This is in his pulitzer winning Guns, Germs, and Steel.

I hope this helps.

I don’t know but it’s too bad. Somehow a
herd of deer or mountain goats doesn’t hold a candle to a herd of elephants sweeping majestically across the savana. Ditto the
poor excuse we have in the New World for
nonhuman primates, compared with the African great apes.

The climate argument might be viable. Europe also lost its mammoths, woolly rhinos,
and sabertooths (though not its regular lions in Greece until historic times), while
megafauna did persist in warmer AFrica and Asia.

Until recently, the Americas had fauna that compared with Africa, and bettered modern African wildlife in many ways. There were at least five species of mammoths and mastodons in North and South American, a giant bison, giant ground sloths, an armadillo the size of a Volkswagon, and wolves and bears and lions big enough to eat all these critters.

Around ten thousand years ago, the last ice sheets retreated from the Americas. This change in climate put a lot of stress on populations, and human hunters arrived on the scene at just about the same time. This combination of environmental pressure and skilled predation was enough to cause the collapse of the entire megafaunal ecosystem.

Details and timelines are still being worked out. (The African animals did not suffer as badly from human hunting because they were learning how to avoid us at the same time as we were learning how to hunt them.)

Dr. Fidelius, Charlatan
Associate Curator Anomalous Paleontology, Miskatonic University
Projector Emeritus, Grand Academy of Lagado
“You cannot reason a man out of a position he did not reach through reason.”

I think Dr. Fidelius is on to something. Learning about floral species, I was taught that North America has many fewer species than equatorial South America because since the latter region has been colonized for a really long time by plants. North America, by contrast, has only been recaptured from ice for a few thousand years, so fewer plant species have arrived, or evolved.

The same goes for animal species. Large animals cover large ranges, and there is simply no huge region in the Americas that has not recently been covered in ice. Compare that to Old World, where a species could conceivably range on all coasts of the Mediterranean, far down into Africa, plus a huge chunk of Asia. Lions were once found in Asia (before the tigers killed them all?) and Southern Europe (before the Romans killed them all?)

A large species in the Americas would probably be confined to one half or the other, since the isthmus is so … isthmian (granted, the Afro-Asiatic connection isn’t exactly huge, but crossing the Sinai/Suez region seems to have been done more than crossing Panama). This just means less territory to roam in, and a smaller area to be confined to when the ice chases down competing species.


Hopefully, I can convince you to accept “hopefully” as a disjunct adverb.
Frankly, I would be lying if I said I were confident.
Perhaps this subject is simply too complex for me to explain.
Unfortunately, I would be lucky to explain my way out of a paper bag.

::Test Post:: Please ignore this post. If there are multiposts above, please ignore them too.

All well and good for the northern regions, but what of South America? Besides the jaguar, it lacks any large mammalian predators, and even the herbivores are confined to goat and deer species of a smallish size (well, and llamas as if those were impressive). As Javaman pointed out, the monkeys of Central/South America don’t hold a flame to the great apes or even some of the Old World’s monkeys.

(not trying to be a pain, I just noticed some of you took ‘New World’ to mean the U.S. and Canada)


“I guess one person can make a difference, although most of the time they probably shouldn’t.”

In African Exodus by Stringer and McKie, 1997, pp. 165-168, is a little "New World " map with semi-circles coming down from the nowthwest and ending at the tip of S.A. These semi-circles: “Martin’s view of the spread of humans through the Americans, and the associated waves of mammal extinction.”

“Martin became (and still is)convinced that the Clovis poeple were responisble for the fact that at least 75 species including…”
And that the exceptions were those large animals what came across the land bridges when the humans did were the ones to survive. They had previous experience of humans and knew how to better defend themselves.

P. Martin: quoted in P. Ward, 1995, "The End of Evolution.

As if the incoming humans ate off all the largest animals first - sounds good to me!


Are you driving with your eyes open or are you using The Force? - A. Foley

Jophiel says:

South America got a double whammy. Remember that, in evolutionary terms, at least as far back as the beginning of the Cenozoic, the important division has been north/south, between Laurentia (north) and Gondwanaland (south). South America was originally part of Gondwanaland, and had a Gondwanalander fauna (ratites, marsupials, edentates). It was connected to North America about three million years ago by the rise of the Isthmus of Panama, allowing the mingling of fauna from North and South America. As seems to be the general case when the two faunas meet, the North American/Laurentian largely outcompeted the South American/Gondwanalander fauna, and drove them into extinction. The remaining South American megafauna then were exterminated by climate change and/or invading proto-Amerinds, leaving such unimpressive specimens as the Virginia opossum and various armadilloes (which have found a new ecological career as road waffles in recent decades).


“I don’t just want you to feel envy. I want you to suffer, I want you to bleed, I want you to die a little bit each day. And I want you to thank me for it.” – What “Let’s just be friends” really means

What happens when populations (of really large animals)find themselves isolated on islands? The Irish Elk comes to mind-it was enormous 9larger than any extant species) and had an enormous rack of antlers. These creatures died out perhaps 12,000 years ago. Yet, the wooley mammoths survived (on Wrangel Island in the Arctic) until quite recently. Does the genetic variability of isolated species decrease-and is this what causes these isolates to die out?

Gould on the link between the arrival of (Maori) humans and the extinction of the New Zealand moa, a large, flightless bird: “Who could resist a 200 pound chicken?”

I’ve definitely heard of this happening. In fact, a case could be made that this is what happened with the aboriginal peoples of the Americas. Not that they went extinct, of course, just that they were more vulnerable to diseases that European visitors shared so generously. But I admit that that’s pretty far from your original point.

On the other hand, isolation can be what saves obsolete species from extinction. (I know “obsolete” isn’t a real biological term, but it’s the best approximation I could think of.) There is that one kind of sea-lizard - the only surviving marine reptile, IIRC, that lives in the Galapagos. There are all those marsupials confined to Australasia. They exist as relics of the evolutionary past, because the more “modern” species can’t reach them to outcompete them. So then when folks bring rabbits to Australia, the onslaught begins.

The persistence of the African megafauna presents a problem with the above theories. Many sub-Saharan Africans have had metal weapons since 500BC - 0BC (I am a little shaky on that date) and seem to have had much higher population densities than were found in the New World and they did not threaten their megafauna with extinction until they had firearms.

North America has gone through at least 4 major glacial periods and subsequent thaws over the last 2.5 million years. I do not believe that the earlier episodes resulted in major extinctions due to climatic stress or reduction of range.

I, too, have seen the radiating frontier of extinction originating up by the Bering Straits as mentioned above. The combination of climatic stress AND human predation might have caused the extinctions. There might be another explanation.

I think it was 20 years ago that the maverick paleontologist Robert Bakker pointed out periods of dinosaur extinction (including the Big One) occured whenever land bridges formed. As was pointed out above, the rising of the land bridge between North and South America was devastating to SA animals because of NA predation. However, Bakker’s theory about the dinosaurs was that disease comes across the land bridge.

If some animal also came across the land bridge at the same time as the proto Clovis humans (12000BC) and had a Eurasian disease for which the natives had no resistance (where have you heard this before?) you would also see the radiating pattern of extinction from the Northwest. Perhaps buffalos had immunity while the camels, mammoths, mastodonts, horses, camels, giraffes, etc, fell victim to some megafaunally morbid variety of flu or AIDS.

This removes the need for the Clovis people to have performed the Herculean task of killing all those critters with stone tipped spears. I an’t see how a band of Clovis people could be more predatious (?) than a continent full of saber-toothed cats.

This is a picture I want to see:“Perhaps buffalos had immunity while the camels,
mammoths, mastodonts, horses, camels, giraffes, etc, fell victim to some megafaunally morbid variety of flu…” all carrying those little boxes of kneenex sneezing their brains off and spreading those grems by the mega-buckets full.

Martin’s map looks pretty convincing.


Are you driving with your eyes open or are you using The Force? - A. Foley

The people are still here and the tigers aren’t. You do the math.

It’s almost certain that all the megafauna of the new world disappeared because humans arrived on the scene and ate them all. The megafauna of North and South America, Australia, Madagascar, Hawaii, New Zealand, Indonesia, and Ireland all disappeared within a few decades or centuries of human arrival. These events were spread out over millenia and the only common factor was human immigration.

When humans were first developing in Africa and Eurasia, the animals that lived alongside them had the opportunity to evolve defenses against the growing human hunting abilities. Animals living in the Americas and other human free areas did not evolve these defenses. When humans with their fully developed abilities moved into these areas, it was a one-sided contest.

One final factor is that most modern people underestimate the hunting ability of humans. One biologist pointed out that even if humans were no more intelligent than dogs they would still be one of the most powerful predators on the planet based on their physical abilities alone. Single humans, unarmed and naked, have killed lions, bears, wolves, and elephants (admittedly, all of these events were extraordinary). But when you add in humans’ abilities to hunt as a group, make tools, and use their intelligence, it’s surprising any species of worthwhile prey survived.

Hey Little Nemo, are you serious about the unarmed and naked humans killing elephants and bears thing? I’m not saying you’re wrong, I’ve just never heard of such a thing. What are some examples of that? Does this mean I can go big game hunting with nothing but my Speedo?

Hi Again, Boris B. Pygmies killed and still kill elephants with a spear. It’s a question of having “right stuff” to stand there and let the elephant get close enough to put the spear in the right place.

“…pygmy hunters wait for the elephant to charge and then they spear it, dodging out of the way at the very last moment…” From The Great Human Diasporas by Cavalli-Sforza and Cavalli-Sforza, 1995, pp2.

Wear the Speedo but take a spear.


Are you driving with your eyes open or are you using The Force? - A. Foley

One note: The arrival date of humans in the new world is far from concrete. Discoveries in the last 10 years have made all but the most conservative anthropologists (i.e., those with tenure) throw up there hands and say “we don’t know, call back in ten years after we’ve had tiome to process all this $^&* data.” It does seem more and more lilely that man first arrived 20,000 years ago or so, and that groups from all over continued to trickle over in a steady stream.

However, the big event that did happen c. 12,000 years ago was the development of Clovis culture–most specifically, the development of a heavy, sharp spearpoint that could be very firmly attached to a staff. Once introduced, this technology spread like wildfire. It leaves much more physical evidence than the culture(s) that proceded it–the evidence of Monte Verde, the best documented pre-Clovis site indicated that those people, at least, used mostly bone and wood products, things that only survive 15 millenia under extraordinary circumstances. Once we thought that the Clovis people had moved across the continient at an unvbelievable rate–now we think that this new technology was spread to the people that were already there (Hey, Vern! Check out this new way to make a spear point! Cool, Sam! I’m gonna run south and show it to Dwight! Clovis points are easy to make once you’ve seen one).

Note this dosen’t really challenge the idea of human-linked mass extinctions, just suggests that technology ws the critical factor, not merely being human. On the other hand, it creates a problem for the germ theory–it now appears that the landbridge was passable and was passed for millenia, not for a brief (centuries) long moment in which the one and only band of American ancestors scurried across.