Natural selection, nature kills the weakest

[Pythagorean]

Huh, I didn't think climate was that stable. Interesting.

 

[DaveC426913]

Huh, I didn't think climate was that stable. Interesting.

For evolution, we're talking a climate that has to be harsh enough, long enough to be a powerful evolutionary driver. Simply put, whether Africa is stable or not, it sure wasn't wiping out populations maladapted for cold.

 

[Evo]

I guess if you assume Africa had two million years of good weather!

Being a tropical country, it's a pretty safe assumption, yes.

Related to Sarah Palin, are you? :tongue2:

Did anyone get the joke?

 

[Ken Natton]

I've been reading the wiki on the human evolution timeline since Ken's last post. It looks like Homo Erectus is who were talking about. They were apparently the first to use fire but it's unclear when.

I’m sorry in advance if I assume too much Pythagorean, but I catch a hint that this story catches your interest as deeply as it did mine. If I’m right, here is another little gem, related to this point about the diverse, concurrent, interdependent changes, and it might just blow your socks off, it certainly did mine. My difficulty is that I do remain conscious of, and perfectly accepting of the importance of, this site’s determination to preserve the scientific rigour of what is here asserted. And this time, my source is neither popular scientific book nor popular science TV programme. It is one of the other contributors I previously discussed this with, someone who clearly knew what he was talking about, and I believe but cannot be certain, was a professional in some capacity. If there is any flaw in what I state here, then it is undoubtedly my misinterpretation, and I can only hope that one of the visitors to this forum who know more than me can tidy up the errors and omissions.

In any case, this is the point: Across the range of placental mammal species, if you correlate average body mass with average brain mass and average gut mass (by which I mean digestive organs, stomach, intestines etc.) the relative masses are remarkably consistent. All except for one species, and I don’t suppose you’ll be the least bit surprised to learn that the species that is off the graph is Homo sapiens. Apparently, our brain is about one kilo heavier than expected, and our gut is about one kilo lighter than expected. Now, I don’t know if it is proven to the degree required to be regarded as scientific fact, but it is difficult to avoid the feeling that the two must be related. Surely it is powerful evidence, at least, of the importance of our changing diet in driving the far reaching changes that our ancestors underwent.

Quite separately, I have previously seen mention of the fact that our ancestors had a much more powerful lower mandible than we do. This heavy lower jaw required a big muscle to control it, a muscle that severely limited potential brain size. A change in diet that allowed a much lighter lower jaw also allowed for the reduction in this muscle and so provided more space for a larger brain. It is clear that we do not have the digestive equipment for raw meat, so meat eating was largely dependant on the facility to break proteins down by cooking. But when I put it to my correspondent that protein consumption was the key to it, this is what he said:

‘gram for gram carbohydrate and protein provide the same amount of energy. but the carbohydrate food our distant ancestors would have been collecting would take a fair amount of effort to collect and digest. also there is the question of fat. while any prey animals would not have the amount of fat that modern domesticated breeds do there would be some. certainly around kidneys and other internal organs and the fatty brown adipose that lies around the spinal column. gram for gram fat provides more than double the energy of either carbohydrate or protein. not a fashionable notion but bear in mind our distant ancestors were not couch potatoes.’​

 

[Pythagorean]

Ken there are two particular milestones that I've always been interested in.

Firstly, the transition from single celled to multiple celled (so I'm of course really fascinated with slime molds, haven't come across similar examples yet.)

The other is the human brain. I remember watching a special (hosted by a Baldwin, I believe) that mentioned the jaw bone - brain connection.

Another interesting thing I remember from that show was the speculation that there was a correlation between us eating meat and being able to afford the high energy requirements of higher thinking that better optimized hunting strategies.

 

[thorium1010]

One thing i would like to point out is that a profound or transformation change might have occurred when we started to cook our food, that means energy required for digestion was reduced and probably directed to the more complex brain.If you look at other animals they spend a lot of time (and energy) for digestion of food . perhaps the growth of brain or its complexity was brought about by cooking our food. Or it could be just a part of the many changes that homo species was adapting in order to survive.

 

[NobodySpecial]

if you correlate average body mass with average brain mass and average gut mass the relative masses are remarkably consistent. ... Apparently, our brain is about one kilo heavier than expected, and our gut is about one kilo lighter than expected.

Except for people from

No too easy, and it's christmas