A new study suggests that human evolution took place in a landscape with significantly more biodiversity than the one we live in today.
The study compared the fossil records of mammal communities in eastern Africa taken from as early as 7 million years ago.
Compared to data taken from 200 present-day mammal groups, researchers found the earlier ecosystems supported a much greater degree of biodiversity.
An artist’s interpretation of an ancient megaherbivore, Gomphotherium pyrenaicum, which once contributed to a greater biodiversity in east Africa.
In particular, earlier times had much larger populations of megaherbivores, plant-eating mammals weighing at least 2,000 pounds such as elephants.
According to the study, picked up by Human Evolution News, megaherbivores have simple digestive systems that weren’t able to efficiently absorb nutrients.
To compensate, these animals had to eat large quantities of food, typically grasses and other plantlife.
The fossil record shows a gradual shift in animal population began around 700,000 years ago.
At this time a larger population of ruminants–animals that have compartmentalized digestive systems that allow more nutrients to be absorbed from food, such as cows and antelopes–entered the fossil record.
The last remaining megaherbivores in Africa today are the hippopotamus, giraffe, elephant, white rhinoceros, and black rhinoceros.
Researchers suggest this shift was driven by the gradual reduction of grazing land as wildfires became more prevalent and reduced food sources necessary to support the larger creatures.
‘These ancient herbivore communities were probably consuming far more vegetation, which means less fuel for wildfires,’ John Rowan, the study’s co-author and a postdoctoral researcher at University of Massachusetts Amherst, wrote.
‘Because fire is an important part of modern ecosystems in Africa and favors grasslands over woodlands, it’s going to fundamentally alter how things are working at the level of entire ecosystems, starting with the plant communities.’
WHEN DID HUMAN ANCESTORS FIRST EMERGE?
The timeline of human evolution can be traced back millions of years. Experts estimate that the family tree goes as such:
55 million years ago – First primitive primates evolve
15 million years ago – Hominidae (great apes) evolve from the ancestors of the gibbon
7 million years ago – First gorillas evolve. Later, chimp and human lineages diverge
5.5 million years ago – Ardipithecus, early ‘proto-human’ shares traits with chimps and gorillas
4 million years ago – Ape like early humans, the Australopithecines appeared. They had brains no larger than a chimpanzee’s but other more human like features
3.9-2.9 million years ago – Australoipithecus afarensis lived in Africa.
2.7 million years ago – Paranthropus, lived in woods and had massive jaws for chewing
2.6 million years ago – Hand axes become the first major technological innovation
2.3 million years ago – Homo habilis first thought to have appeared in Africa
1.85 million years ago – First ‘modern’ hand emerges
1.8 million years ago – Homo ergaster begins to appear in fossil record
800,000 years ago – Early humans control fire and create hearths. Brain size increases rapidly
400,000 years ago – Neanderthals first begin to appear and spread across Europe and Asia
300,000 to 200,000 years ago – Homo sapiens – modern humans – appear in Africa
50,000 to 40,000 years ago – Modern humans reach Europe
Source : Mail Online