Human evolution; savannah theory fading (Introduction)

by dhw, Tuesday, July 12, 2022, 08:52 (647 days ago) @ David Turell

DAVID: The point still is, and you haven't changed it, we evolved to use all sorts of environments in a warm jungle area (AFRICA) and then migrated all over to every climate on the Earth to easily adapt. The jungle origin did not provide that degree of adaptability for future use. The new big brain did just that and appeared in advance of migrations as the article shows.

dhw: The “point” of the article actually shifts from the origin of bipedalism to much wider considerations, and you have chosen to focus on the brain, but the sentence I have bolded moves in the same direction. The brain - which incidentally is a community of cell communities - had the (perhaps God-given) ABILITY to adapt and innovate, and it used this ABILITY to cope with and exploit new environments. Why do you say the “new big brain”? The early ancestors “dating from around 7 to 5 million years ago” had tiny brains compared to ours! We know that the brain responds to new requirements by complexifying, and so each exploitation/innovation (possibly triggered by migration to new environments), would have increased the brain’s complexity and in due course created the need for greater capacity. We needn’t go into the subject of expansion here, as we have dealt with it repeatedly elsewhere, but quite clearly our earliest ancestors’ brains can only have evolved into new bigger brains AFTER (and I would say as a result of) “their first tentative steps as bipedal mammals in tropical forests, or at least mixed forest habitats”.

DAVID: The erectus brain developed in Africa and the erectus wandered all over the Earth handling new environments with ease. You can talk all around that without changing the import of that history. The brain came before all the required uses in subsequent migrations.

Why have you suddenly skipped millions of years and hominins and homos? The subject is human evolution. Our history reaches back millions of years to small-brained hominins who apparently still lived in forests, although it is possible that their environment was mixed. Lucy’s brain capacity was about 400 cc. What you call the “new big brain” was the result of expansion over millions of years as hominins and homos encountered new conditions and environments. We know the brain RESPONDS to new requirements. When you say: “The brain came before all the required uses”, yes, the little brain was there from the start, and it gradually became bigger as it learned to cope with or exploit new conditions, but Lucy was not born with the “new big brain”! Even erectus wasn’t born with the “new big brain”, since his/her brain appears to have expanded from approx. 850 cc to 1000 + cc. I’d hoped to avoid a repetition of our discussion on brain expansion, but you still seem to be hooked on the notion that every expansion was a divine dabble IN ANTICIPATION of new requirements.