Human evolution: Neanderthal Y chromosome (Introduction)

by David Turell , Monday, September 28, 2020, 15:26 (1299 days ago) @ dhw
edited by David Turell, Monday, September 28, 2020, 15:34

DAVID: Hominins and homos were in small population numbers before we advanced 50,000 years ago and began to build a large population. This fits Gould's concept of small isolated populations causing rapid or large evolutionary advances.

dhw: Hence my proposal that sapiens may have branched off from the apes because local conditions may have forced particular groups to descend from the trees, whereas elsewhere the apes were able to carry on as before.

DAVID: Well, what does fit is that the early forms walked upright while still having heavy tree climbing upper body and small brains. You appeal to a natural cause while I favor God.

dhw: What do you favour? Did your God preprogramme upright walking semi-apes, or did he step in and do a dabble on the legs, leaving chests and brains alone until the next dabble? Why do you think he would preprogramme or dabble these interim changes? What purpose would they have served unless it was to meet some new requirement?

DAVID: As usual you view it backwards to my approach. Upright posture allowed hands to become more dexterous, which in and of itself, will drive develop of new requirements in the activities that could be performed. Humans have the ability to invent new activities for themselves.

dhw: You have not answered my questions! But yes, our views are directly opposite. As I understand it, your theory is that your God fiddled with our ancestors’ anatomy BEFORE they descended from the trees. I propose that they descended for a reason, and their anatomy changed as a RESULT of their spending more time on the ground. I would also propose that life on the ground provided them with more opportunities to use their hands, which became more dexterous as a result. It’s not clear to me whether you think your God fiddled with their hands as well as their legs. It’s the same problem as with the whale’s fins and the human brain. You have your God preprogramming or dabbling every change in anticipation of new requirements, whereas I propose that fins and enlarged brains are the result of new requirements.

No need to change or repeat my known answers. God designs what is needed for each new advance, anticipating new abilities and activities.

DAVID: But first all were groups of apes using trees. Do trees suddenly disappear over night? No, it was gradual, which means the ape groups could easily followed the retreat of the trees. Your natural theory, as usual, has huge holes.

dhw: You have just agreed that isolated populations cause large evolutionary advances. An isolated group of apes would be isolated for a reason. They would not “easily follow” anything that took them out of their isolation. But of course this is all speculation. Maybe tree life wasn't providing enough food for our little group of explorers. Or maybe there was too much competition. Meanwhile, I’ll be interested to hear your answers to my questions above.

DAVID: Answered.

dhw: Not answered. Nor have you responded to my argument concerning isolated populations.

Isolated populations are also subject to deleterious mutations which destroy the group.

Answered several days ago in a comment you removed in your next reply:

Saturday, September 26, 2020, 11:22 (2 days ago) @ David Turell

QUOTE: Neanderthals had smaller populations than moderns, and small populations tend to accumulate deleterious mutations, especially on the X and Y sex chromosomes. (David’s bold)