A Bad Day Off East Africa-Around 3 Million Yrs Ago

DaleCoz

This is from the May 1999 issue of my Alternate History Newsletter, but I never posted this scenario online.

What actually happened: I read recently that paleontologists in South America have discovered that a rather large asteroid impact occurred off the west coast of South America sometime around 3 to 4 million years ago. They can date it more precisely, but I don’t have the reference with me. The impact wasn’t big enough to be a planet killer. It may have had some effect planet-wide, but any worldwide impact was not on the scale of the dinosaur extinction. It was far enough away from the centers of human development in East Africa that our ancestors were only modestly affected. They went on about the business of discovering fire, developing language, and generally becoming a pain in the butt to essentially every other land animal.

On a continent-sized stage, in South America, this asteroid strike may have been extremely devastating. There are fossil beds from the period with thousands of land and sea animal skeletons jumbled together, probably from enormous tidal waves generated by the strike. The heat from the strike would have ignited grass and forest fires over a large part of the continent, although the Andes Mountains would have shielded the rain forests of the Amazon to some extent. The climate on and around South America would have been chaotic for weeks or months. Did all of this lead to widespread extinction in South America? Probably. I’ll look into that in more depth later.

What might have happened: Change that asteroid’s history just a tiny bit—not enough that it misses earth entirely. It hits a few thousand miles east of where it hit in our time-line. That puts it off the East Coast of Africa. Animals in that section of the world have a very bad day. Then the few that survive in the area have a very bad couple of months while the climate settles down and the vegetation grows back. Their problems are increased by the fact that the vegetation of the region changes temporarily. Forests are temporarily replaced by grasslands, and animals adapted to those grasslands flood in, shouldering aside forest and savanna-adapted survivors. Those survivors are for the most part restricted to areas where little patches of the old vegetation survived. The range of proto-humans is restricted to the hard hit area.
 

DaleCoz

Some big issues: There are actually several big issues here. First, if proto-humans go extinct or don’t develop sapience because of this, how does it impact the rest of the earth? Does anything ever develop sapience, or do the animals of earth remain animals until the sun goes out? What impact, if any does the fact that South America’s ecology is much more intact have? I’ll get into those issues later, but I’ll start by looking at the immediate consequences of the strike.

Immediate Consequences—Africa: Large predators are hit very hard at first. They are at the top of the food chain, but that makes them very vulnerable to any disruption below them. Predator populations drop fast, but even if some predators become locally extinct they are all widespread enough that they can easily repopulate the disrupted area from other parts of Africa or even from Asia or Europe if necessary.

Primates are very hard hit, especially large ones. Most primates require forests. The ones that don’t require forests still climb trees to elude predators. Forests take a long time to recover after they’ve been burned off of nearly half a continent. A few primate species that are restricted to East Africa go extinct in those few months after the strike. A few more are so hard hit that they are on the brink of extinction. Populations drop so low that inbreeding becomes a problem. They linger on the edge of extinction as the scars from the impact heal.

Within a couple thousand years, a zoologist miraculously transported to the area would be hard-pressed to point to any major changes brought about by the strike. Local predators may have lost a subspecies or two. A couple of species of primates died out completely, but closely related species from outside the area quickly take their place. The odd ground-living species of apes from East Africa are on the verge of extinction, but they never were very common anyway. Other than the fact that they may have been our ancestors in this time-line, they are not particularly significant. Monkeys have been encroaching on their niches for the last five to ten million years. The surviving species are a tiny and declining remnant, probably slated for extinction in five or ten million years anyway. Even before the asteroid strike, they were rare enough to be almost invisible in the fossil record.
 

DaleCoz

Madagscar gets hit very hard. The Elephant Birds—ten-foot-tall 900-pound birds that took on the role of deer, cows, and horses in Madagascar—die out completely. The biggest predators in Madagascar die out. So do quite a few of the largest primates. The large, slow, leaf-eating primates become extinct for the most part.

So, nothing much appears to have changed in East Africa. Madagascar got hard hit, but that’s to be expected. Islands are very vulnerable to any kind of abrupt change, and their animals are unique so they can’t be replenished from outside the area. We’ll get back to East Africa later.

Immediate Consequences—South America: I’m going to have to digress a little here to set the scene for the asteroid striking or not striking South America. South America should be of some interest to alternate-biology buffs in and of itself because it asks and answers several interesting alternate biology questions. Try these on:




  • What if Marsupials had taken over the carnivore role and regular mammals had taken over the large herbivore role right after the dinosaurs died out? That happened in South America.
  • What if giant predator birds had developed along the same lines as the small, fast carnivorous dinosaurs? That happened in South America.
  • If you put the ancestors of monkeys, apes, and men on a different continent and reran the last thirty million years, would the results be different? If so, how? That happened in South America.
  • What if rodents started taking over? That sort of happened in South America, at least for grazing and browsing animals.
 

DaleCoz

In South America, not having the asteroid strike might have some interesting results. It’s hard to pin down causality here, because in our time-line the asteroid came at a very interesting time. South America had been an island continent, though not totally isolated, for around 55 million years. It had developed its own very different animals. Think Australia only on a much larger, richer, and more diverse scale. Those unique South American animals were about to meet the animals of the rest of the world head on as the last arm of the sea separating North and South America disappeared.

It is very hard to separate out extinction caused by the asteroid strike from extinction caused by disease and intense competition from invading North American animals. Part of the problem is that some South American groups were on their last legs before the asteroid strike or the invasion from North America.

More Information than most people want to know about South American animals in our time-line: By the time the asteroid hit, South America had already had two major stages of animal development and a minor one.

Stage one: The old South American animals: When South America was first isolated, it had 3 major groups of mammals. A Marsupial group called the Borhyaenids dominated most carnivore niches. Other Marsupials held the niches for seed-eating, rodent-like animals, most of the niches for insect-eating animals, and part of the niches held by monkeys and other primates in the rest of the world. Some very odd and now extinct distant relatives of horses and deer called Notoungulates and Liptoterns dominated the browsing and grazing niches. A group called the Edentata (sloths, anteaters, and armadillos) played a minor role.

Many of these animals looked and acted a lot like animals we are familiar with, though their ancestry was totally different. Carnivorous marsupials probably looked and acted a lot like bears, wolves, and even sabertooth tigers. They chased one and three-hoofed animals that resembled small horses, along with large animals with short trunks like early elephants had.
 

DaleCoz

Stage two: Rodents, Monkeys and Giant Birds: After several million years of isolation, the ancestors of the South American monkeys and rodents arrived, probably by island hopping. They gradually expanded into most, but not all of the niches that monkeys and rodents hold on other continents. At the same time, various groups of old South American animals came into competition. A group of large carnivorous flightless birds grabbed most of the niches for large fast-running carnivores. These birds came very close to reproducing the body form of some of the fast-running small carnivorous dinosaur. Their wings became arm-like, even to the point of redeveloping claws at the tips of two fingers. The Borhyaenids gradually became smaller as the giant birds became more dominant. At close to the same time, groups of Edentata challenged the Notoungulates and Liptoterns for the browsing and grazing niches. Ground Sloths and Volkswagen-sized armadillos became increasingly common.

Stage two-point-one: Raccoons and Giant Rodents: A few million years before the continents connected, a species or two related to raccoons made it to South America. They apparently made life even harder for the surviving Borhaeyinids as they developed into several groups, some of them dog-like and one of them with the size and habits of a bear. Ecologically equivalent Borhyaenids disappeared. At the same time, South American rodents like the Capybaras and their relatives were pushing into the large grazer and browser niches. If you’ve ever seen a Capybara, you probably noticed that it looks like a hundred-pound Guinea Pig with deer-like legs. Similar animals became very common in South America, many of them even larger than a Capybara. The largest ones probably approached the size of a Rhino. Notungulates and Liptoterns species dwindled.

Then the meteor came: Now here we get into a bit more speculation. From what I’ve read, it looks as though most of the large carnivores, including all of the remaining Borhyaenids except for a sabertooth tiger look-alike, died off at or shortly after the time of the meteor strike. Highly predatory opossums developed to fill the vacuum, some of them as big as a fox. I don’t know if any of the giant predator birds or the unique South American raccoons survived in South America after the time of the asteroid strike, though one species of giant predator bird showed up in Florida during the Pleistocene. I suspect that large predators were essentially cleaned out of the southern and western parts of South America, and hit hard on a continent-wide basis. South America is a considerably smaller continent than Africa, and its predators can’t be replenished by similar species from outside the affected area. The impact, if any, on South American primates is unknown.

Then the North American animals flowed in: The continents connected. North American animals swept south, while a few South American mammals flowed north. Ground Sloths from South America became common in North America, moving north as far as Alaska. Armadillos and capybaras became common in the southern US. Dogs, cats, saber-tooth tigers, weasels, bears, deer, llamas, peccaries, horses, mastodons, squirrels, and countless other animals moved south. South American carnivores either already were extinct or quickly became extinct. The only exceptions to that are a few highly predatory opossums that still survive in weasel-like niches in South America.
 

DaleCoz

Now we do some serious speculation—Africa: The fact of the matter is that if the asteroid that hit off of South America had hit off the East Coast of Africa, none of us would be here. In all likelihood, even if humankind survived and even developed along the same lines that we did the results would be different enough that we couldn’t or wouldn’t want to interbreed with them. Even if the ancestors of humanity survived, they would survive with a subset of our ancestors’ gene pool. Would that subset contain the elements necessary for these survivors to seize the opportunities that led to our ancestors going the way that they did? If not, they might survive, but only as a couple of odd east African species of chimpanzee-like critters. Our ancestors would also be vulnerable in another way: if they had developed a primitive proto-culture before the asteroid strike they could lose part or all of that culture as their population goes through a bottleneck as a result of that strike.

For the purposes of this scenario, I’ll assume that our ancestors linger on, in East Africa, but do not progress into anything remotely human for the foreseeable future. Oh, they might gradually develop a better set of tools, or a somewhat better way of communicating, but nothing very out of the ordinary. Three million years after the asteroid strike, and even four million years after it, they are still just odd chimpanzees. Whether they survive or not isn't all that important to the scenario. The important thing is that they never become human.
 

DaleCoz

How does that change the world from around 3 million years ago to now? Well, initially it keeps our most direct competitors and the species most vulnerable to us in the game. Sabertooth Tigers and hunting humans apparently couldn’t coexist. In our time-line, Sabertooths died out in the Old World as humankind spread. Sabertooths survived in the New World until the Paleo-Indians arrived. In this time-line, they survive in Africa as well as Asia and the New World.

Giant Baboons (300 pounds or so) appear to have been very direct competitors with our early ancestors. They became extinct in our time-line but they solidify their hold on part of what should have become our niche in this time-line. They are hit hard by the asteroid strike, but not as hard as our ancestors are by its aftermath. A group of 300-pound baboons weren’t vulnerable to all that many predators even without trees as places of refuge.

Chimpanzees become more widespread and somewhat more advanced than in our time-line. In our time-line, chimpanzees have left the rainforest and colonized more open savanna areas in a few places. That happens when there is a local taboo against people eating chimpanzees. There are some indications that chimps in savanna areas become more vocal than chimps in the forest, and exhibit different kinds of tool use. In this time-line, chimps move out into the savannas in a big way, and start adapting to the demands of the new habitat.

New chimp subspecies form that are better adapted to this new habitat. They offer formidable competition for the beings that would have been our ancestors, but they have specialized enough for walking on their knuckles that it is hard for them to get out of that dead-end. Knuckle walking ties up their hands and limits the extent of their tool use.[FONT=&quot] [/FONT]
 

DaleCoz

There may be some additional species of apes in Africa in this scenario. In our time-line, the fossil record of African apes for the last four of five million years is almost non-existent. Chimps are common in the flesh in our time-line, but very close to nothing has been found of them in the fossil record. It is quite possible that several additional species of apes were hanging on in Africa in our time-line until our ancestors administered the final blow. In this time-line, some of those species would be destroyed by the asteroid strike. Others might linger on.

The two time-lines diverge increasingly as human impact increases in our time-line. In our time-line, wave after wave of human spread out of Africa, with each wave bringing new technology and expanding the human niche. Those waves were accompanied by waves of animal extinction in Asia, then in Australia and North and South America. I have always believed that directly or indirectly our ancestors caused those waves of extinction. That’s a very controversial point of view, but I’ve read a great deal on both sides of the issue and the evidence for humans causing the bulk of those extinctions seems reasonably solid to me.

The rest of this scenario will assume that in the absence of humans most but not all of the large ice age animals that became extinct in our time-line would survive and continue to develop. That means that in Asia at least three species of great apes in addition to the Orangutan survive. That includes Gigantopithecus, the nine-foot-tall ape that may have inspired the Bigfoot stories. Mammoths survive in Siberia, and pygmy species of stegodont (a kind of primitive elephant) survive in the islands between Australia and Asia long enough to colonize Australia.
 

DaleCoz

In Australia, the stegodonts drive the largest species of diprotodonts (visualize a wombat almost as big as a rhino and you can sort of picture diprotodonts) to extinction. They actually help a few of the smaller species of diprotodonts and especially the kangaroos by digging for water when waterholes dry up. Marsupial predators find catching stegodonts a very big challenge, as do Australia’s 20-foot-long, very carnivorous monitor lizards.

In North and South America, the impact of not having an asteroid strike off of South America is being felt. North American animals are having a much tougher time moving into South America when the land bridge is completed, because the South American ecology is much more intact than it was in our time-line. Stegodonts do head south relatively easily and start developing into new species adapted for the jungles and mountains of South America. Llamas and horses eventually head south too. Among North American predators, Sabertooth Tigers move south relatively easily, displacing their marsupial imitator. Other North American predators have a much tougher time. In northern South America, giant predator birds fight fierce battles with the ancestors of jaguars, wolves and mountain lions over carcasses and favored hunting spots. Those fights are reasonably even. A few species of giant birds flow north. A few more North American predators flow south. South American grazers and browsers like ground sloths, giant rodents, and giant armadillos flow north. Several species of opossums and South American monkeys make it as far north as northern Mexico.
 

DaleCoz

By our time-line’s 1999 AD, this time-line’s Africa ends up with several animals with some potential for eventually going down the line that leads to cities and spaceships, but none that have gone more than a short distance down that path. An observer with no emotional baggage would probably pick elephants and their relatives or one of the group of monkeys that includes the baboons as the groups most likely to break out and become the dominant species.

Elephants or closely related species are already the dominant large herbivores almost everywhere on the planet where there are land mammals. In this time-line, unlike ours, elephants have even reached Australia, with a dwarf Stegodont making the final hop from Sulawesa to New Guinea and then across a land bridge into Australia around 40,000 BP. There are even elephants or their close relatives on most of the large islands. They shape their environment, turning forests into open plains by tearing down trees, by digging down to where the water is when waterholes dry up, and even digging deep into the earth to mine for salt. They use simple tools, and communicate over long distances using noises too low for the human ear to pick up. Adult elephants are almost immune to predators. As in our time-line, they form an “anti-predator cartel” with baboons, tolerating baboons because the baboons keen eyesight allows them to spot predators that the elephants can’t. They have enormous brains, far larger than a human’s, though smaller in proportion to their enormous bodies.
 

DaleCoz

Our hypothetical observer would probably also pick some groups of old-world monkeys as having a lot of potential for advancement. Baboons and their relatives are very adaptable and aggressive, and are continuing to spread into new niches. Various species of monkeys have adapted to very cold climate (Japanese monkeys), a semi-aquatic niche (Crab-eating monkey), life as a ground-living, fast-running animal (Patas monkeys). Our hypothetical observer would probably look at the trends and expect Old World monkeys to finish exterminating the few remaining species of apes in a million years or so, then expand into new niches.

In South America, our hypothetical observer would see some animals with potential. The observer would definitely notice the large, partly ground-living spider monkeys that became extinct around the time the first Indians arrived in our time-line. The observer might also see larger, more ground-living species of capuchin monkeys, and notice that they are at least as good with tools as any of the Old World apes.

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DaleCoz

[FONT=&quot]Fast forward 5 million years into this time-line’s future: [/FONT]The great apes like chimps and Gorillas are now extinct, pushed out of the last of their niches by less intelligent but more versatile monkeys. The smaller apes like gibbons and Siamangs still linger on in Asia, but their range is decreasing, and it is becoming apparent that they don’t have much more time before they die out completely. Old World monkeys, on the other hand, are still diversifying into new niches. Some species are becoming more adapted to the cold winters of northern Asia and the southern peninsulas of ice age Europe, even developing a primitive form of hibernation. That puts them in increasingly direct competition with the smaller bears, and those bears become rare.

Old World monkeys still haven’t made it across the Bering Strait into North and South America, but a species of semi-aquatic monkey has made it across the last water gap into New Guinea and Australia. There with no competition from big cats and wolves, it has taken over most of the large and medium-sized mammal predator niches. Packs of fast-running predator monkeys chase down kangaroos and even pull down some of the smaller stegodonts. Other monkey species take up more traditional primate niches in the jungles of New Guinea.

Australia and New Guinea are becoming less and less marsupial lands, as more and more modern mammals make it across the water gaps from Asia. By five million years from now, monkeys. tarsiers, stegodonts, and several waves of rat species have made it to New Guinea and Australia. All of them have generated new species, and in some cases taken up new ways of life. Many of the native marsupial species are suffering. A few marsupial groups are still thriving. Kangaroos are doing very well, as are some of the rat-and-mouse-sized predators and some of the possums.
 

DaleCoz

Monkeys have generated a bewildering array of species in Australia and New Guinea. They are taking over whole areas of the ecology. There are now large browsing and even grazing species that act more like deer than monkeys, though their genetic heritage still shows.

Diprotodonts are nearly extinct, victims of competition with the elephant-like stegodonts on the high end of their size range, and monkeys on the low end. All of the marsupial predators above 25 pounds are already extinct, their niches taken by fast predatory monkeys.

Some species of those monkeys have spread back into southern Asia, where they are providing very tough competition for more traditional predators like dogs and cats.

The larger predatory monkeys in Asia find themselves preying on Ground Sloths. The big sloths only made it as far as Alaska in our time-line, but given an extra five million years they have expanded into Asia in this time-line, and are even infiltrating into northern Africa.

The Ground Sloths are among the very few South American mammals to make it to Asia. Quite a few have made it to North America though. There are a wide variety of large South American rodents roaming North America, some of them weighing up to 300 pounds and acting more like antelopes than mice. Giant predatory birds from South America have also headed north. They are making life difficult for more traditional predators as far north as Oklahoma.
 

DaleCoz

South American monkeys related to the Capuchins have spread north to some extent too. Some species have gotten bigger and taken on baboon-like habits. Others have become fast-running animals of the plains of southern North America. They look and act a lot like the Patas monkeys of Africa, though they aren’t quite as fast. They do have a couple of advantages in their prehensile tails and their ability to manipulate objects.



It looks as though at some point Old and New World monkeys will expand to meet one another and clash in a huge ecological battle spanning continents, but that is still millions of years off. The planet will have to warm enough for primates to cross the Bering Strait, or primates will have to adapt to extreme cold and month-long periods of night.
 

DaleCoz

The new ecology that is developing increasingly emphasizes animals with an ability to manipulate the environment, to form flexible alliances with other species, and to pass information along to other members of their species. No single species in this time-line has developed along those lines as far as humans did in ours, but several species are much further along than any species other than humans in our time-line.



As time goes on, and no one species breaks out to become the single intelligent species in this time-line, the window of opportunity for such a breakout may be closing. At some point as species become more capable of passing some form of proto-culture along it may become increasingly difficult for any one species to generate a critical mass of innovations, because those innovations tend to be imitated by other animals with their own proto-cultures.

Does any one species ever gain enough of a lead over the other species to have a human-like ascendance over them? Does any species ever make it off the planet? At the 5 million years into the future mark there is still no sign of that.
 

DaleCoz

And that's all I wrote. I would be interested in your take on this. If humans went extinct or got mission-killed by an extreme genetic bottleneck around 3 million years ago, what would happen?
 

Workable Goblin

Well, you know about the Toba bottleneck, right? That seems to have been about as bad as your proposed incident (only a couple hundred individuals survived), but obviously humans survived that fine.

Also, for the last bit--what if multiple intelligent species arise roughly simultaneously (close enough that you end up with at least H. Sapiens sapiens-Neanderthal-style conflict)? Perhaps driven by their proto-culture. Or, since it seems certain areas of the world have clearly dominant proto-intelligent species, what if each area gave birth to its own unique intelligence? Eg., New World monkeys in South America, elephants in Australia, baboons in Africa. That could be interesting--there's this whole "alien" thing going on, without even needing space travel.
 
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