Abstract
Among terrestrial mammals, Homo sapiens has evolved a very specific anatomical feature—very little body hair—thus, the skin surface is exposed directly to the environment. We and others have demonstrated that skin epithelial cells, called keratinocytes, express not only functional sensory systems for a variety of environmental responses, but also a series of neurotransmitter receptors that play key roles in information processing in the brain. Furthermore, the brain cortex is particularly large in Homo sapiens, which has a higher ratio of brain to whole-body weight than any other mammalian species. Here we propose that the evolutionary success and global spread of Homo sapiens are due at least in part to the existence and interaction of these two systems; i.e. the epidermis and brain cortex. First, we discuss the role of the epidermis as a sophisticated organ with multiple sensory inputs and information-processing capabilities, and then we consider the putative requirement for a large brain to carry out simulations and predictions based on input from multiple epidermal systems. We also present some other examples where a functionally sophisticated epidermis is associated with a large brain size. Finally, we discuss possible reasons why Homo sapiens has emerged as the sole surviving human subspecies.
Highlights
Surface coverings of living things have generally evolved to offer a survival advantage in their natural environment; for example, reptiles have protective scales, birds have feathers that are used to control flight, and terrestrial mammals have insulating body hair
What special advantage(s) do humans derive from their hairless skin? Could the combination of hairless skin and a large brain account for the evolutionary success of Homo sapiens? did this unique combination contribute to the successful spread of Homo sapiens across the globe into an enormous range of environments, from hot, ultraviolet-B-enriched deserts to arctic regions?
We suggested that hairless skin offered an evolutionary advantage, because it was more efficient at sensing danger signals from the environment, because its sensory systems are more accessible
Summary
Surface coverings of living things have generally evolved to offer a survival advantage in their natural environment; for example, reptiles have protective scales, birds have feathers that are used to control flight, and terrestrial mammals have insulating body hair. Homo sapiens evolved certain unique anatomical features—including loss of body hair—which exposed the skin surface directly to the environment, leaving only a water-impermeable membrane, the stratum corneum, at the outermost layer of the skin, as protection. Another unusual anatomical characteristic of Homo sapiens is a large brain, especially the cerebral cortex section of the brain. We suggest that denuded epidermis receives and processes environmental information in real time This input initiates emergency action when required, while being passed on to the brain, where it is utilized for simulation/prediction to guide future action, which in turn could be modified by sensory feedback. It is plausible that the epidermis generates huge amounts of information about its environment
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
