The ancient non-human primates that gave rise to humans and modern humans are primates with relatively sparse and patchy body hair, soft-to-very-soft shallow-layered skin, and thin-boned limbs. The common ancestor of humans and chimpanzees, for example, which lived between 6 and 8 million years ago, was likely covered in vegetative body hair and had thicker and stronger skin than humans, but with other important similarities to modern humans such as a bipedal stance and very flexible our hands.
assistant
The closest primate relative to humans known by scientists to have had tough and thick skin are our common ancestors which are estimated to have lived as recently as 18 million years in the past. Ongoing fossil research provides increasing support for a group of extinct primates called the Australopithecines, which lived between about 4.2 and 2.5 million years ago, being our closest evolutionary relatives. Australopithecines were terrestrial apes living in forest and woodland environments in East Africa, similar in size to modern gorillas. The skin of lower and upper limbs was similar in structure to that of modern apes, while that of the trunk was also well-buffered with fat and collagen and covered in well-organized, intermeshed and slow-growing hair. Australopithecine skin structure becomes more human-like over time, evolving to become thinner and less hair-covered to adapt to our increasing dependence on bipedal walking and tool use, and our increased capacity for cultural development
assistant
Is there a simple reason why human skin is so much weaker than nearly all animal skin? Even if you compare us to primates, we have thinner flesh. Did we develop this way due to domestication or were our distant ancestors like this even when they lived in the wilderness?
user
Human skin does indeed have a relatively thin and fragile structure, which makes it especially vulnerable to human injury and disease. But our macroevolutionary starting point was the tough and thickly skinned animals that lived in the wild. Over the course of humans’ evolution, our skin evolved to become thinner, less hair-covered and more sensitive, due to selection for skin that is more flexible and energy-efficient in human societies. Human skin evolved to become more fine-grained to help us adapt to tool use, larger exchange of information through symbols and other cultural developments, and decreased exposure to environmental hazards. However, this increase in sensitivity leads us to be more delicate and to develop skin diseases more easily. This is likely an evolutionary trade-off due to the advantages of our cultural development.
assistant
What is our closest ancestor that we know of who likely had tougher flesh?
user