Large mammals shaped the evolution of humans

Large mammals shaped the evolution of humans

Subject :Science and Technology

Section: Biotechnology

Context: It was the abundance specifically of medium and large grazers in fertile savannas, concentrated near water in the dry season, that enabled the evolutionary transformation of a relatively puny ape into a feared hunter in Africa.

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• That humans originated in Africa is widely accepted. But it’s not generally recognised how unique features of Africa’s ecology were responsible for the crucial evolutionary transitions from forest-inhabiting fruit-eater to savanna-dwelling hunter.
• Ape-men
  • Starting during the late Miocene, around 10 million years ago, a plume of molten magma, hot liquid material from deep inside the Earth, pushed eastern parts of Africa upward. This led to rifting of the Earth’s crust, volcanic eruptions and soils enriched in mineral nutrients from the lava and ash.
  • Grassy savannas spread and animals adapted increasingly to graze this vegetation
  • Apes from that time were forced to spend less time up in trees and more time walking upright on two legs.
  • Progressive reductions in rainfall, restricting plant growth and worsening dry season aridity, forced the early ape-men, (Australopithecines), to change their diet. They went from eating mainly fruits from forest trees to consuming underground bulbs and tubers found between the widely spaced trees.
  • This led to the emergence through evolution of the genus Paranthropus (colloquially “nutcracker man”), characterisedby huge jaws and teeth.
• Homo habilis
  • Around 2.8 million years ago, another lineage split off from the australopithecines, used stones chipped to serve as tools. These were used to scrape flesh from carcasses of animals killed by carnivores, and crack open long bones for their marrow content.
  • These first humans thus became scavengers on animal left-overs. They most probably exploited a time window around midday when the killers — mainly sabre-tooth cats — were resting, before hyenas arrived nocturnally to devour the leftovers.
  • To facilitate such midday movements, Homo habilis lost its body hair; this made it possible for them to be active under conditions when fur-covered animals would soon over-heat.
• Homo erectus
  • Several hundred thousand years of progressive advancements in upright walking and brain capacity led to the next major adaptive shift, stone cores became shaped on both sides to aid the processing of animal carcasses.
  • This led to the emergence of Homo erectus around 1.8 million years ago. These early humans had become efficient hunters. Consequently, meat and bones became reliable food resources year-round.
  • Men hunted; women gathered plant parts. This required a home base and more elaborate forms of communication about planned excursions, laying the foundations for language.
• Homo sapiens
  • After 800,000 years ago, fluctuations in heat and aridity became more extreme in Africa. Finely crafted stone tools defined the transition into the Middle Stone Age, coupled with the emergence of modern Homo sapiens in Africa around 300 thousand years ago.
  • But despite its hunting prowess Homo sapiens had declined to precarious numbers in Africa by around 130,000 years ago, following an especially severe ice age.
  • Genetic evidence indicates that the entire human population across the continent shrank to fewer than 40,000 individuals, spread thinly from Morocco in the north to the Cape in the far south.
  • One remnant survived by inhabiting caves along the southern Cape coast, exploiting marine resources. This reliable food source fostered further advances in tool technology, and even the earliest art.
  • The use of bows and arrows as weapons, along with spears, probably contributed crucially to the expansion of humans beyond Africaaround 60,000 years ago. They spread onward through Asia and into Europe, displacing the Neanderthals.
• Thus, if Africa had remained largely low-lying and leached of nutrients like most of South America and Australia, this would not have been possible.