14 DAY TRIAL // Modern human families are pleased with having one, maybe two children at a time and per total, but for early humans success was determined by their capacity to produce many, as many as possible, offspring.
Low reproductive ability combined with competition might have led to the extinction of early human species. "The lineages of primates have some traits that make it hard for them to respond to rapid perturbations in the environment," says Dr. Nina G. Jablonski, professor of anthropology and department head at Penn State. "Through time we see a lot of lineages become extinct when environments where the species are found become highly seasonal or unpredictable."
Primates emerged in the Paleocene and Eocene when the global climate was less seasonal, fact that allowed them low reproductive rates. But in Pliocene, 5 million years ago, the climate changed, turning seasonal, and large patches of forest were replaced by savanna, bringing many primate species to extinction. "While past primate populations moved with the forest, early hominid cultures 2.5 million years ago show signs of the ability to live in marginal areas and live on more dynamic, seasonal landscapes," said Jablonski.
Human lineage evolved, occupying a wide variety of biotopes, but those too specialized could not resist to climate changes. Paranthropus boisei, a hominid that reached its peak 2.5 million years ago, disappeared one million years ago due to competition with other mammals. P. boisei would have been too specialized on tough food items like seeds, tubers and bones.
For this kind of food, it competed with pigs and hyenas, but Paranthropus produced one offspring yearly at most, while its competitors had large litters, growing their populations at a much faster rate. "We find that the early members of the genus Homo who succeeded were super ecological opportunists," says Jablonski. "They would eat vegetation and scavenge, kill small animals and forage."
Another victim of specialization seems to have been the Neandertal people. They resisted well from 200 to 50,000 years ago, but about 26,000 years ago they disappeared. "Neandertal was extremely adept culturally," says Jablonski. "They had big brains, a wide variety of tools and were extremely successful as active, aggressive hunters of large game. We see evidence of hunting, kill sites, butchery and even herding off cliffs. We find thrusting spears and butchering knives."
In a warm interglacial period, before the last glaciation, about 18,000 years ago, the grassy plains disappeared, taking with them the large game (like mammoths, reindeer, woolly rhino, musked ox), the prime food source for Neandertal, that needed vast steppes.
Modern Homo sapiens, too, were deprived by large game, but they were not equally affected as they could fish, or hunt small animals like rabbits, turtles and birds. "Rather than being a specialized large mammal predator, modern humans would eat anything they could get their hands on. They eked out a living even if it meant eating grasshoppers or whatever," says Jablonski. "Even with this, modern humans barely hung on from 12 to 16,000 years ago. Why did Neandertal not adapt culturally? Why did they not start eating bunnies? They did begin fishing."
Perhaps when Neanderthals started cultural changes, it was already too late. "I think they were out-competed at the very end. Modern humans simply did it better, more nimbly."
And another thing: Modern people have the capacity of storing food and water, an ability that Neanderthals seem to have lacked. The higher plasticity of the modern humans must have boosted its reproduction compared to Neanderthals, widening the space of the single birth race between species. "Can we, today, control our cultural behavior to ensure our environmental success. Can we control growth and population density, or come up with new technology to overcome the problems we will face from the global climate change we have created? We clearly have the cultural ability to do either." said Jablonski. "But both require forethought and planning to face the demographic and climate change. A degree of honesty, our species is not known for."
Image credit: Rama