Analysing footprints that fossilised about 1.4 million years ago, scientists believe that the responsibilities of women and men were already separate in early human social life in the Pleistocene epoch. The information was given in a report by the British news organisation The Telegraph.
The footprints left by eight hominins in mud around what is now Lake Turkana in Kenya had been preserved for a very long time. Recent research has found that all the members of the group were male, and that they belonged to Paranthropus boisei, an ancient human species.
The new research has also found that their height was the same as that of Homo erectus, which lived in the same area. It is still not known for certain why a group of only males set out together. But because there are no footprints of women or children, researchers believe there was a division of responsibility between men and women in certain tasks or expeditions.
In the societies of today’s great apes, too, males take part in guarding an area as a group, defending boundaries and hunting. A co-author of the study and researcher at Harvard University, Dr Neil Roach, said the movement together of eight adult male Paranthropus boisei, with no females or children present, points to a complex social structure in the species.
He said they probably lived in large groups. Although there would have been competition among the males for mates, they tolerated and also cooperated with one another for safety in a dangerous environment. Paranthropus boisei was a species of the australopithecine group, which lived in East Africa between about 1.15 million and 2.5 million years ago.
Although they are not direct ancestors of modern humans, they are a species that arose from the same predecessor. They later took a different evolutionary path and became extinct.
Before the discovery of these footprints, most information about Paranthropus boisei came from fossils of their skulls with large jaws and teeth. There was very little information about the physical structure of the body below the neck. From their thick bone structure it had previously been assumed that the average height of the males was about four and a half feet.
But researchers analysing the footprints with two-dimensional and three-dimensional technology, and observing the structure of the feet and the pattern of movement, found that they were much larger than had been assumed.
The size of these footprints is almost the same as that of Homo erectus footprints, although Homo erectus had until now been thought to be much larger in size.
A researcher at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, Dr Kevin Hatala, said the size of the footprints shows that their body structure was like that of modern humans. Their height could have been up to six feet and their weight about 75 kilograms.
He said it was a surprising result for the team. But it was also true, he said, that knowledge of the part of the body below the neck in this species had been very limited, because most of the fossils found so far were only skulls and teeth.
In his words, fossil footprints are the only evidence that gives a direct idea of the social behaviour of an extinct species. He added that it suggests they lived in groups with many male members, and that cooperation among adult males was an important part of their social strategy.
Researchers analysed volcanic ash in the surrounding rock layers to date the footprints to about 1.43 million years old. A total of 21 footprints have been identified, believed to be from eight individuals. Footprints of hippopotamus, deer and various other animals have also been found.
The footprints were first found about 50 years ago by a researcher at the Smithsonian National Museum of Natural History, Dr Kay Behrensmeyer. They were later preserved under sand for future research. They have recently been analysed afresh.
Dr Behrensmeyer said the greatest scientific feature of footprints is that they preserve a particular moment. She said people can also relate far more easily to fossils of the past through footprints than through an isolated bone or jaw.
Over the past few decades, hundreds of hominin footprints spanning more than a hundred thousand years have been found in the eastern Lake Turkana region. Paranthropus boisei was the same size as Homo erectus; this new information has raised new questions about why the species became extinct.
Dr Behrensmeyer said it was not possible to say what kind of contact there was between the two species in that muddy area. But it is known that they were present there at the same time.
She added that when the footprints were first found in 1978, no one imagined it would grow into so large a collection or give so broad a picture of the life and environment of early human groups.
বাংলায় মূল প্রতিবেদন পড়ুন · Read the original Bengali report