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Natural selection hard to measure?

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You mean the same way that  ghosts in the barn loft are hard to find?

From Evolution News & Views:

Charles Darwin’s idea that an unguided natural process led to all the beauty and diversity of the world, including its Undeniable appearance of design, guides scientific thinking to this day. But what if his signature mechanism — natural selection — cannot be measured? Without measurement, a theory reduces to anecdote. A recent paper in the Proceedings of the National Academy of Sciences threatens to do that, at least in regard to “the evolution of human body form.” The implications go far beyond human physiology.

Consider limb length. Say you want to deduce how natural selection has affected the dimensions of the femur bone. The authors point out that one cannot measure directional selection on one bone without taking into account how all the other bones are affected.More.

The late Lynn Margulis probably offered the most succinct summation of natural selection: Not all life forms that come into existence can survive.

Apart from the need to preserve Darwinism (natural selection acting on random mutations) as a pretended mechanism for the production of information, when it is wholly improbable, that fact does not point to any specific pattern about which life forms will survive or what information they will develop or retain.

The future of evolution lies in discovering actual mechanisms, not hypothetical ones.

See also: What the fossils told us in their own words

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Mung, Cumulative selection is just selection over many generations (so this generation get's the advantage of the last several generations of selection). So, what do you think Bob's example lacks? wd400
"The future of evolution lies in discovering actual mechanisms, not hypothetical ones." The soul creates information (out of nothing) by acts of free will. It is a miracle. The soul is primary cause, not secondary cause. It is not a mechanism. We can create information (do miracles) only because we are created in God's Image. Erasmus Wiffball
Who is the author at Evolution News and Views? Seems like someone who just processes words superficially. No understanding of the analysis in the journal article. Not that I can see. Would you take medical advice from someone named Anonymous? No? Then why take opinionated explanation of science from someone named Anonymous? Erasmus Wiffball
Bob O'H. You're describing selection, not cumulative selection. Mung
Mung - there are a lot of experiments where you start with a population, subject it to a selection pressure (e.g. a particular temperature or food regime) and measure a response (e.g. body size) over several (e.g. 20) generations. If there is a heritable response to selection, then the trait will change cumulatively (if there is a response but it is not heritable, then you will only see one generation of change). To make any inference more solid, this is typically done with several replicate populations, and also done using several regimes (e.g. high/low temperature, or high/low food), so differences in response to selection can be looked for. What (hopefully!) happens is that there is a consistent change in phenotype: all populations in one regime go in one direction, and all in another go in another direction. Bob O'H
Hello Bob O'H, If I were at "the skeptic zone" I'd ask for a rigorous definition of cumulative selection and what is the unit of measure used to measure it, but I'll not require that of you. :) But could you briefly describe such a selection experiment and how you think one might measure cumulative selection in such an experiment? Is it anything like deciding to drive from Philadelphia PA to Washington DC and measuring your progress in miles as they accumulate, knowing what your target is in advance? Or is it more like just watching a certain number of members of a population which have a certain trait increasing in time while another trait decreases in the population over time? Because that's just plain old selection. cheers Mung
If natural selection is hard to measure, cumulative selection must be near impossible to measure.
Actually, it can be easier. It's why people use selection experiments over several generations - differences will accumulate due to selection, so become easier to see. Bob O'H
If natural selection is hard to measure, cumulative selection must be near impossible to measure. There's a standing challenge over at TSZ for all the Weasel lovers to come up with an objective measure of cumulative selection. So far no takers. Mung

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