New Miscellany 2: intelligence, savannah, the Cambrian (General)

by David Turell , Tuesday, March 25, 2025, 17:46 (9 days ago) @ dhw

Intelligence

The savannah theory

DAVID: With the new findings the savannah theory has been diluted from primary importance.

dhw: How many more times? The new findings tell us nothing about where, when or why our ancestors first descended from the trees. Who decides what is of “primary” or “secondary” importance? Do you think the savannah theory is of secondary importance compared to your belief that one fine day your God popped in to operate on the legs and pelvises of a group or groups of tree-dwellers?

God did it is just as valid as the savannah theory.

Human origin from different groups

QUOTE: Fossil evidence suggests that species such as Homo erectus and Homo heidelbergensis lived both in Africa and other regions during this period, making them potential candidates for these ancestral populations

DAVID: this extensive study tells us how various hominins may have mixed to make us as the sole surviving form. It does not satisfy dhw's quest for a full theory as to the development of bipedalism.”

dhw: We covered this theory last Thursday and Friday. You have stated categorically that we are descended from Erectus, so I’m really not sure where this theory leads us. It certainly doesn’t lead to the start of the process, and our discussion began with your belief that the savannah theory was fading, though you now acknowledge that it is a logical explanation.

It is one of several theories.

Theoretical origin of life: diurnal stress

Oxygen levels rising and plunging:

https://www.sciencealert.com/extreme-feast-and-famine-cycle-sparked-explosion-of-life-o...
QUOTES: "Imagine a world where the oxygen you need changes dramatically between day and night.

"Now, picture early animals trying to survive in such an extreme environment. This was the reality for early animal life in oceans and seas about half a billion years ago. This was also the time when animal diversity boomed, in what is known as the "Cambrian explosion".

"Daily swings in oxygen levels on the shallow seafloor may have stressed early animals (the ancestors of all animal life today), pus hing them to adapt in ways that fuelled diversification."

DAVID: for once, a logical set of reasons for developing early life forms. Today's extremophiles show how they modify to handle stressful environments.

dhw: Your headline is way off track. This is an explanation of the Cambrian Explosion! And it’s good to see that you accept not only the ability of extremophiles to modify themselves, but also that of the ancestors of all animal life today, which would include ourselves. The changes enabling these life forms to survive would have had to be very rapid, or they could not have survived. So for once you now you have “a logical set of reasons” for the Cambrian Explosion.

Diurnal stress is exactly the story's point! It is no explanation for all the Cambrian forms with eyes, brains, limbs, etc. from no precursors.