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What prompted primitive man to become bipedal?


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Bumf said

 

"I doubt that the wearing of clothing would be the only reason why man's ancestors lost their fur. "

 

It is not the only reason. In any evolutionary development like this, we have to look at two sides to the change.

1. What is the adaptive advantage of the change?

2. How does the organism overcome the adaptive disadvantage of the change?

 

For loss of fur, there are two main adaptive advantages often suggested - improved cooling, and improved resistance to parasites. However, that does not answer the question as to why human are the only terrestrial mammal in our size range to go furless. The reason other mammals have not is that they cannot meet point (2) - they cannot overcome the selective disadvantage of going furless. And that disadvantage is, of course, loss of thermal protection, which we get with clothing.

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Bumf said

 

"I doubt that the wearing of clothing would be the only reason why man's ancestors lost their fur. "

 

It is not the only reason. In any evolutionary development like this, we have to look at two sides to the change.

1. What is the adaptive advantage of the change?

2. How does the organism overcome the adaptive disadvantage of the change?

 

For loss of fur, there are two main adaptive advantages often suggested - improved cooling, and improved resistance to parasites. However, that does not answer the question as to why human are the only terrestrial mammal in our size range to go furless. The reason other mammals have not is that they cannot meet point (2) - they cannot overcome the selective disadvantage of going furless. And that disadvantage is, of course, loss of thermal protection, which we get with clothing.

 

I'd completely agree that clothing did have some sort of effect on ancient man to have lost their fur but I highly doubt it was the precursor to it. Most likely man began losing his fur, began moving northward where it is cooler and clothing use began to increase (or perhaps began spending most of their time in lakes and rivers to cool down?). However I personally believe that overheating of the body due to the change of environment in that area was the major change that lead to it. Actually they could all have occurred simultaneously.

 

I think the question to ask at this point is 'why were they overheating?'. I'm fairly certain that the climate change wouldn't have been the only reason because, as you said, there are still animals in that area that have fur covering their body even today. Most likely a lifestyle change occurred at the same time. Now what kind of lifestyle change would have to occur to a creature to have such a vast effect, most likely due to the change in climate?

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Another thing that would have helped us go furless is our big brains. Less fur means we need extra metabolism, or extra metabolism means we need less fur. Because our big brains use so much energy, they would increase our metabolism and lower our need for fur. Probably a minor effect though.

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One possible explanation for pre-human fur loss might be the same reason some human males lose hair today. One type of male boldness is due to an enzyme in the scalp that can't break down testosterone. If we extrapolate this, then the pre-human males increased testosterone beyond what the enzymes of the fur cuticles had been designed for. This, in turn, could be connected to why humans began to breed all the time. Human do not have a breeding season, any time is the right time.

 

In the poorest countries the number of babies is high because there is a high mortality rate. It makes sense the pre-humans had to breed more often for the survival of the species, due to unfavorable circumstances that created a high infant mortality rate. This increased testosterone in the males due to getting busy more often. These genes are then transferred.

 

Walking up right may have also been a necessity due to a type of natural event that created the need to migrate into maybe desert areas they had little instinct for. They had to learn as they went with the result, a lot of problems, at first, that may have resulted in the high infant mortality.

 

With this area of evolution we often think in terms of the males. It is interesting when you think of the females. They don't have clubs. Their hands have babies. When she was more like an ape on all fours, the baby could hang underneath in the shade. Walking upright creates exposure to the sun. It is almost like a medley of mishaps that works out.

 

I am still of the belief the pre-humans were not that bright. Animals don't just leave a nice ecosystem unless they are forced to. The branch of the ape tree that still remains, didn't have the same push into the future. I would also assume it was not easy, but very tough for them. This is where they were forced to adapt faster than if they had been in a cosy environment. Necessity is the mother of invention.

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