Human evolution: presents another huge gap II (Introduction)

by David Turell , Thursday, November 11, 2021, 05:12 (896 days ago) @ David Turell

"To understand this challenge, let’s consider a seemingly simple example. In 2004 a study in Nature proposed that a single mutation that inactivated a protein could cause “marked size reductions in individual muscle fibres and entire masticatory muscles” leading to “loss of masticatory strength,”8 which could have loosened jaw muscles, allowing our brains to grow larger. A news story widely circulated, titled “Missing link found in gene mutation,” framed the finding this way: “an ancient genetic mutation for weaker jaws helped increase brain size, a twist that first separated the earliest humans from their apelike ancestors.” The story sounds plausible, but there’s more to it. Leading paleoanthropologist Bernard Wood noted that this mutation alone could never have provided a selectable advantage, and would have required additional changes:

"The mutation would have reduced the Darwinian fitness of those individuals. … It only would’ve become fixed if it coincided with mutations that reduced tooth size, jaw size and increased brain size. What are the chances of that?

"We thus have a situation where multiple coordinated mutations would be necessary to provide the advantage. Yet a 2008 population genetics study in Genetics found that to obtain only two specific mutations via Darwinian evolution, “for humans with a much smaller effective population size, this type of change would take > 100 million years.” The authors admitted this was “very unlikely to occur on a reasonable timescale.” In other words, when a trait requires multiple mutations before an advantage is gained, it would require more than 100 million years within a species such as ours.

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"...he misses another major opportunity to point out a serious deficiency in the evidence for human evolution: the lack of fossil evidence documenting a transition from the ape-like australopithecines to the human-like Homo. This “gap” in the fossil record is well attested in the literature.

"One Nature paper noted that early Homo erectus shows “such a radical departure from previous forms of Homo (such as H. habilis) in its height, reduced sexual dimorphism, long limbs and modern body proportions that it is hard at present to identify its immediate ancestry in east Africa”11 — or anywhere else for that matter. Another review similarly notes, “…it is this seemingly abrupt appearance of H. erectus that has led to suggestions of a possible origin outside Africa.”12 Likewise, a paper in the Journal of Molecular Biology and Evolution found that Homo and Australopithecus differ significantly in brain size, dental function, increased cranial buttressing, expanded body height, visual, and respiratory changes, stating:

"We, like many others, interpret the anatomical evidence to show that early H. sapiens was significantly and dramatically different from… australopithecines in virtually every element of its skeleton and every remnant of its behavior."

Comment: Please see part I. This comes from a critical review of "In Quest of the Historical Adam", by William Lane Craig, recently published.