Archaeologica.org

http://www.sciencedaily.com/releases/20 ... 135043.htm

If you think summer in your hometown is hot, consider it fortunate that you don't live in the Turkana Basin of Kenya, where the average daily temperature has reached the mid-90s or higher, year-round, for the past 4 million years. The need to stay cool in that cradle of human evolution may relate, at least in part, to why pre-humans learned to walk upright, lost the fur that covered the bodies of their predecessors and became able to sweat more, Johns Hopkins University earth scientist Benjamin Passey said.

The bit about walking upright because of the heat feels like a bit of an evolutionary stretch.

Minimalist wrote: The bit about walking upright because of the heat feels like a bit of an evolutionary stretch.

Definitely a stretch. Fur, for sure. But the entire skeletal structure and organ re-org required to walk upright? I'd doubt it to be anything more than a minor contributory factor.

Maybe standing upright created more surface area of epidermis and thus more sweat glands through which to cool. Other than that and internal organ spacing, I don't see why walking upright would be any more advantageous in the heat than climbing a nice tree or finding a cool cave.

They even noted it at the end. The same climate that was so hot was thinning the trees. Once you can't swing from tree to tree anymore than you have little choice but to get down on the ground. It's dangerous on the ground. There are big cats with sharp teeth. Standing up to look around would have definitely given an evolutionary edge.

Minimalist wrote:They even noted it at the end. The same climate that was so hot was thinning the trees. Once you can't swing from tree to tree anymore than you have little choice but to get down on the ground. It's dangerous on the ground. There are big cats with sharp teeth. Standing up to look around would have definitely given an evolutionary edge.

Ahhh. I didn't think about thinning trees. Early predator detection is a far more impactful selection than heat avoidance. Seriously, though...mid 90's for 4 million years? West Texas suddenly seems less hostile.

Try Arizona!

Minimalist wrote:Try Arizona!

I spent a day in Kingman once, out on the edge of the desert. My fur fell out and I suddenly started walking more erectly. The desire to master fire and use more complex tools quickly followed.

Minimalist wrote: The bit about walking upright because of the heat feels like a bit of an evolutionary stretch.

So how about putting it to the test? Simultaneously measure the outside temperature, in the sun, at 2 feet and at 5 feet above the ground, above the same spot. Record the values. Repeat every day. See if there's a difference.

Temperature is an important and sensitive factor for the human body. 0,5 (C) of a degree makes the difference between a normal state and a fever. Scrotums are there because human semen develops better at 1 or 2 degrees (C) below the 37 C of the average human body.

Johnny wrote:

Minimalist wrote:Try Arizona!

I spent a day in Kingman once, out on the edge of the desert. My fur fell out and I suddenly started walking more erectly. The desire to master fire and use more complex tools quickly followed.

I was through Kingman when I went to Las Vegas. The "desert" was lush and green because of all the rain/snow we had up there this year.

I figure sometime in the next two weeks it will catch fire and burn forever.

Scrotums are there because human semen develops better at 1 or 2 degrees (C) below the 37 C of the average human body.

I'm dying to know how you know that!

So how about putting it to the test? Simultaneously measure the outside temperature, in the sun, at 2 feet and at 5 feet above the ground, above the same spot. Record the values. Repeat every day.

It's been done RS, and there is an advantage to upright walking under hot conditions, but to suggest that that is a cause rather than a result is a step too far for me.

Roy.

Minimalist wrote:

Scrotums are there because human semen develops better at 1 or 2 degrees (C) below the 37 C of the average human body.

I'm dying to know how you know that!

Junior high

Come on. I barely recall going there....let alone anything they said.[/quote]

Well, funnily enough: I do! They teach all kinds of amazing, interesting and worthwhile stuff at elementary and high school, you know. Not just at college. And I paid attention. I guess that must be why I'm a rokcet scientist while you ain't!

Besides: haven't you, in all your 60 years, ever noticed that your scrotum shrinks and expands continuously, all day every day, under influence of the outside temperature? Because that is its function! It's basically a temperature regulator! To keep your nuts at the ideal production temperature under all circumstances! So it changes/adapts when the circumstances do!

The explanation that I have always seen was that an upright bipedal posture presents less body area to be heated by the sun, vs a more horizontally oriented quadrapedal posture...

Besides: haven't you, in all your 60 years, ever noticed that your scrotum shrinks and expands continuously, all day every day,

Must be a Dutch adaptation.

circumspice wrote:The explanation that I have always seen was that an upright bipedal posture presents less body area to be heated by the sun, vs a more horizontally oriented quadrapedal posture...

Yes, I guess that was a factor as well.
There's never just one reason for evolutionary change. It's always a combination of factors.

Minimalist wrote:Standing up to look around would have definitely given an evolutionary edge.

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