Why do we humans have less hair than our ape ancestors? What evolutionary event could make hairless

advantage?

Why do we humans have less hair than our ape ancestors? What evolutionary event could make hairless skin an ..

The main reasoning is because homo sapiens originated in hot, dry climate areas. There was no real need of fur/hair. However, the more north we went, the more hair we accumulated.

Also, don't forget, that we have hair all over our bodies. It may not be thick or colored, but it's there when you look through a magnifing glass.

Why do we humans have less hair than our ape ancestors? What evolutionary event could make hairless skin an ..

Man's discovery and utilisation of fire for heating and cooking food. Also the use of skins and furs as clothing.

Why do we humans have less hair than our ape ancestors? What evolutionary event could make hairless skin an ..

We don't actually have less hair - it's just that the hair we have is much finer and thinner than that found in the other great apes.

The reason for this is one of the big questions in the evolutionary history of humans.

Theories include increased ability for evaporative cooling (more skin to sweat, and be cooled by sweat) as we moved from the forests onto the savanna.

Another theory is that it is due to adapting to a semi-aquatic lifestyle at one point - that humans lived on the shores of lakes, rivers or sea, and swam and waded in the water to catch sea critters. This would explain our relative hairlessness, our ability to swim (most great apes can't), our seemingly instinctual affinity for beachfront areas, as well as the development of our extremely agile fingers, and even tool use (to break open shells - as sea otters do). It has the disadvantage of having no fossil or archaeological evidence to support it.

Another theory is that it has to do with species identification - much like different plumage in birds. It allows us to quickly identify a human even from a distance.

Some of this might be answered if we knew exactly when we developed the hairless trait: Was it early in our hominid history (i.e. Australopithecines?) or was it only much, much later, say for example that it is only a trait of anatomically modern humans? Unfortunately, fossils don't preserve the hairiness of our ancestors, so it's impossible to say right now, except for speculations.

Why do we humans have less hair than our ape ancestors? What evolutionary event could make hairless skin an ..

I'm basically cutting and pasting my answer to a similar question from last week...

It's been awhile since I've read much of the literature on this, but there was considerable anthropological work done on this issue in the 1960's and 1970's.

Anyway, the general consensus is that evaporative cooling (sweating) only works well if you aren't really hairy. So as far as body hair goes, generally we'd do better in a Savanna environment without hair. While it's possible to cool yourself without evaporative cooling (e.g., panting of lions and so on), we happened to have gone this other route, and now we're "stuck" with the results so to speak.

As to the hair on the tops of our heads... at least three entertaining possibilities that I recall. First, our heads would be more exposed to sunlight than any other part of our body and thus are subject to burns (ask any bald guy). Hair protects skin from burns, and so retaining scalp hair would be beneficial that way. I believe there was some good circumstantial evidence that supported this idea in the 70's... Some one measured hair density on bodies and concluded that shoulders and backs were essentially second for hairiness among peoples in relatively warm climates. Anyway, fun hypothesis for head hair had to do with giving babies something to hang on to while riding on mom or dad's back. This is a bit far fetched today, but might not've been 500,000 years ago or so, in which case our hair is simply a retention of a primitive trait. Last but not least... there's always the catch-all "sexual selection" hypothesis (one gender strongly preferred hair on the head, and thus the rest of us are stuck with it).

If you're looking for other, related things to research, we're also more oily than other mammals (sebaceous glands occur at high densities), certainly more sweaty, and we have a relatively strong obsession with personal grooming.

Why do we humans have less hair than our ape ancestors? What evolutionary event could make hairless skin an ..

Your question is backwards. Natural selection does not act on traits that are absent. The relevant question to ask is what advantage does hair give to humans? The answer is none--at least under circumstances where people are capable of making clothing, fire, and shelters. So, humans that lacked genes for hair were not at a reproductive disadvantage.

Since the lack of hair almost necessitates development of skills that allowed humans to compensate for loss of skin protection, lack of hair likely coincided with increased intelligence, and it is likely that increased intelligence is what gave modern humans a selective advantage over earlier forms.

At the same time, hair can be a selective disadvantage because it harbors all sorts of parasites and pathogens. Humans with less hair may have had a lower mortality rate from diseases and parasites associated with hair.