Arthur Smith

https://sandwalk.blogspot.com/2014/05/answering-creationist-questions-about.html Ten years ago. Some good comments, including Joe Felsenstein.

A skeleton found in Gough's Cave, Cheddar (of the cheese), UK recently had remnants of DNA extracted and sequenced. According to press reports, this fully modern human, when living around 10,000 years ago, had dark skin and blue eyes. Fixation by drift? Sexual selection? Niche change and population explosion from neolithic to now? ETA: and there's no reason to suppose "either or" here. Ah, missed that. There was a discussion on Larry Moran's blog a while ago that might be of interest.

Sure. But I would find it difficult to remain optimistic, even though it is the outcome I expect. Where are they? Anyway, the hiatus between yule and New Year will soon be over so much less time for me to comment. Happy New Year everyone.

Sorry, I corrected the link. Extrapolation may be justified, I suggest. What if the mission brings back evidence of micro-organisms fundamentally unlike that found on Earth? On that basis, separate abiogenesis events on two adjacent planets in one solar system, abiogenesis seems inevitable given the right range of conditions.

It refers to the ongoing Mars Perseverance mission, of which one objective is to return physical samples to Earth. The article discusses possible results from examining those samples and the implications.

Not sure if this blog post from 2021 is still valid or if budget cuts will cause the venture to be cancelled.

I wonder if the claimed positive effect of random genetic drift could be (or has been) measured. The hypothesis I imagine would be something like "Under the effect of selective pressure on a population of sexually reproducing organisms, a locus with fewer alleles lost to drift will move to fixation in fewer generations than a locus with more variants". Consider population 1. A gene is fixed in the population of 100 and 1 beneficial allele enters the gene pool. Consider then population 2 (also 100). A locus has 10 neutral alleles at 10% frequency and 1 beneficial allele enters the gene pool. Is the rate of selection of the beneficial allele going to be different between population 1 and population 2, all else being equal? You, me and Sir Arthur Eddington. 😉

It wouldn't surprise me that evolvability would be a trait subject to selection. Yes, it is my view that drift is not an adaptive process but becomes insignificant in large populations. I'm not quite sure what you mean about energy and entropy in this context. Certainly one attribute of known living entities is that they maintain themselves out of thermal equilibrium with their immediate environment by using an available energy source

Indeed. Drift is the process by which an allele (a variant of a gene) will fix in a sexually reproducing population in the absence of selective pressure. The effect is noticeable, particularly in small populations lacking genetic diversity, and often results (or contributes to) in loss of a species by extinction. Perhaps it would be an idea for commenters to identify what sort of evolution is being referred to. Biological evolution seems to be the subject of the thread, but there is also cultural evolution and using evolutionary algorithms to solve problems such as the evolved antenna. 1. Why not list them, then, for clarity? 2. Disagree. But I am open to correction by an example. 3. There's nothing complicated about the idea of selection in biological evolution. Darwin categorized three sorts of selection: artificial, natural, sexual. The process is change in allele frequency in all those cases. 4. Not really. I would use the word "niche". 5. Allele variation and fixation can be a slow process where generation times are long, but evolution can be fast enough to be observable. Here is a classic. 6. Yes, biological evolution can be outstripped. Rapid climate change is a disaster for many species. Mass extinction events are unfortunate for those caught up in them, but the subsequent opportunities for survivors got us here.

Well, I don't dispute that random genetic drift happens (or at least convincing models exist in the sphere of population genetics). But the clue is in the "random" bit. In small populations, genes may fix randomly which leads to loss of diversity and extinction. Resulting empty niches may be opportunities for other populations (the Chicxulub bolide did that for mammals around 65 million years ago) but without selection change does not produce the fit of species to niche. You need that feedback for change to be adaptive. I'm curious to learn of other ways that feedback can lead to an evolutionary process. Goodness me. All life on Earth, ALL life, is on the same branching tree. Admittedly the roots are a little tangled but the evidence is overwhelming. Perhaps I should make a distinction between shovels and entities such as biological organisms that reproduce. Tool use (not restricted to humans) evolves adaptively. If you want to access tubers, a stick is handy. A stick that doesn't break is better, a hardened point more so. Observing and learning from others even better. The bias is stronger when the learning is retained over generations. Human cultural evolution has swamped human biological evolution.

Not sure how much broader the idea could get. Selective bias on populations of reproducing individuals leads to change in time over those populations. Works with shovels, Covid virus, Great Auks, computer memory.

Yes. Evolution requires a selective bias for adaptive change to take place. Drift does not introduce selective bias. Your demand for a definition of "agency" may be perhaps answered by a selection process.

In small populations, random genetic drift results in loss of allelic variation, which in turn can lead to extinction. I guess the empty niche left is an opportunity for another species. I'm yet to be convinced of how else drift contributes to adaptive evolution. Would that not be artificial selection?

Asking as a dyed-in-the-wool adaptationist, what other mechanisms can be substituted for selection that produce change over time?

Any explanation for the site being off-line? ETA: never mind. Failed to scroll.