Early pre-humans (Evolution)

by David Turell , Thursday, August 31, 2023, 22:41 (239 days ago) @ David Turell
edited by David Turell, Thursday, August 31, 2023, 22:50

David: "Comment: this leads back to dhw's criticism of God's work. In a past discussion dhw wondered why God bothered to create so many pre-sapiens forms. My answer as usual is God prefers to create by evolution of living organisms, and in the universe by using a multitude of stars to create the original 92 elements, while the Earth evolved as life appeared on it."

"Here is a new study on pre-sapiens forms and how few remained after a deep freeze 900,000 years ago:

https://www.sciencenews.org/article/extreme-cold-human-ancestors-population-crash-dna

"Human ancestors nearly died out between around 930,000 to 813,000 years ago in an evolutionarily pivotal population bust, a contested new study concludes.

"This potential winnowing of human ancestors into a barely sustainable number of survivors coincided with a period of extreme cold and extended droughts in Africa and Eurasia, previous geologic evidence indicates.

"If the new DNA-derived scenario holds up, relatively few survivors of the Stone Age big chill may have evolved into a species ancestral to Homo sapiens, Neandertals and Denisovans, say population geneticist Wangjie Hu of the Icahn School of Medicine at Mount Sinai in New York City and colleagues. Previous analyses of DNA extracted from ancient fossils estimate that this common ancestral species appeared between around 700,000 and 500,000 years ago. (my bold)

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"Hu’s team devised a new statistical method to estimate the timing and sizes of ancient breeding populations using patterns of shared gene variants in human populations today. The modern genetic data came from 3,154 people in 10 African populations and 40 European and Asian populations. Hu’s group obtained that information from two scientific databases of human DNA.

"The scientists calculated the expected diversity of these modern variants based on hypothetical ancient population histories, some of which included periods of drastic declines in numbers of breeding adults. A population crash among human ancestors that lasted from about 930,000 to 813,000 years ago best accounted for the genetic variation in the analyzed data, the researchers conclude.

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"As that diminished population began to rebound, its members may have evolved into H. heidelbergensis, Hu’s group suspects Some researchers regard H. heidelbergensis as an ancestor of Denisovans, Neandertals and H. sapiens that first appeared around 700,000 years ago in Africa and Eurasia. But other scientists say that fossils assigned to H. heidelbergensis contain too many skeletal differences to qualify as a single Homo species. (my bold)

Note: https://www.newscientist.com/article/2390124-our-ancestors-may-have-come-close-to-extin...

"The early humans alive at this time have been assigned to a number of different species, including Homo heidelbergensis, Homo rhodesiensis, Homo antecessor and Homo bodoensis, and it is unclear which of these is our ancestor. There is also debate about whether they were indeed separate species."

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"Present-day human DNA analyzed in the new study has been studied and modeled for years by other investigators, none of whom have cited any signs of such an ancient, steep population decline, Schiffels says.

"But severe climate shifts could potentially have pushed human ancestors and other species close to or over the brink of extinction, says population geneticist and study coauthor Ziqian Hao of Shandong First Medical University in Jinan, China. In the Aug. 10 Science, another team — including Ashton and Stringer — described ancient climate reconstructions indicating that a previously unrecognized cold phase in Europe led to sharp declines in hominid numbers about 1.1 million years ago.

"Hu and colleagues plan to incorporate ancient hominid DNA and a larger sample of present-day human DNA, especially from Africa, into further analyses of ancient population ups and downs."

Comment: For pre-human species we may be splitting instead of lumping! This suggests a pattern God uses to winnow down diversity of form and numbers. The cold snap loss of forms and the loss of dinosaurs are such a pattern. dhw constantly questions how God did things, but we arrived, and it is obvious, retrospectively that He knew exactly what He was doing.