Difference between revisions of "Haldane 1937"
(→Page 338) |
|||
| Line 9: | Line 9: | ||
=Notes= | =Notes= | ||
| − | + | ==Page 337== | |
| − | ==Paragraph One== | + | ===Paragraph One=== |
Haldane points out the distinction between Darwinian evolution (novel adaptation) and stabilizing selection (or purifying selection or "maintenance" selection) that removes mutations which result in a phenotypic change. | Haldane points out the distinction between Darwinian evolution (novel adaptation) and stabilizing selection (or purifying selection or "maintenance" selection) that removes mutations which result in a phenotypic change. | ||
| − | ==Paragraph Two== | + | ===Paragraph Two=== |
The change in frequency of alleles resulting in novel adaptation can be very slow in human terms; however, extremely fast on a geologic timescale. Very small fitness differences in numbers of offspring could be virtually impossible to detect by direct observation yet have a very real evolutionary effect. | The change in frequency of alleles resulting in novel adaptation can be very slow in human terms; however, extremely fast on a geologic timescale. Very small fitness differences in numbers of offspring could be virtually impossible to detect by direct observation yet have a very real evolutionary effect. | ||
| Line 23: | Line 23: | ||
It is implied that two samples of size ''n''=8,000,000, half with the genotype and half without, would be compared for a total of 16 million. | It is implied that two samples of size ''n''=8,000,000, half with the genotype and half without, would be compared for a total of 16 million. | ||
| − | ==Paragraph Three== | + | ===Paragraph Three=== |
Again, adaptive evolution is expected to be very slow and not observable on a time-scale of human lifetimes (however, today we know of exceptions to this where observable evolution can happen quite rapidly). Except, Haldane says, possibly in cases of adapting to changes in the environment many of which are human caused, "agriculture, fishing and industry". "The balance of nature has recently been upset in a manner probably without precedent in our planet's history; and hence on the Darwinian theory we should expect that evolution was proceeding with extreme and abnormal speed." | Again, adaptive evolution is expected to be very slow and not observable on a time-scale of human lifetimes (however, today we know of exceptions to this where observable evolution can happen quite rapidly). Except, Haldane says, possibly in cases of adapting to changes in the environment many of which are human caused, "agriculture, fishing and industry". "The balance of nature has recently been upset in a manner probably without precedent in our planet's history; and hence on the Darwinian theory we should expect that evolution was proceeding with extreme and abnormal speed." | ||
| − | ==Paragraph Four== | + | ==Page 338== |
| + | ===Paragraph Four=== | ||
The observation is made that in spite of selection against less fit (mutant) individuals in a species, and that this reduction in fitness is heritable, these individuals continue to appear at a roughly constant frequency over time, implying a deleterious-mutation-purifying-selection equilibrium. | The observation is made that in spite of selection against less fit (mutant) individuals in a species, and that this reduction in fitness is heritable, these individuals continue to appear at a roughly constant frequency over time, implying a deleterious-mutation-purifying-selection equilibrium. | ||
| Line 33: | Line 34: | ||
==Terms== | ==Terms== | ||
| − | + | *Facies - appearance. https://en.wiktionary.org/wiki/facies | |
| − | Facies - appearance. https://en.wiktionary.org/wiki/facies | ||
[[Category:Publication]] | [[Category:Publication]] | ||
Revision as of 01:02, 10 September 2018
Contents
Citation
Haldane, J. B. S. (1937). The effect of variation of fitness. The American Naturalist, 71(735), 337-349.
Links
- https://www.journals.uchicago.edu/doi/abs/10.1086/280722
- https://www.jstor.org/stable/2457289
- http://hawaiireedlab.com/pdf/haldane1937.pdf (internal lab link only)
Notes
Page 337
Paragraph One
Haldane points out the distinction between Darwinian evolution (novel adaptation) and stabilizing selection (or purifying selection or "maintenance" selection) that removes mutations which result in a phenotypic change.
Paragraph Two
The change in frequency of alleles resulting in novel adaptation can be very slow in human terms; however, extremely fast on a geologic timescale. Very small fitness differences in numbers of offspring could be virtually impossible to detect by direct observation yet have a very real evolutionary effect.
"In order that an observed viability difference of 0.1 per cent. should exceed twice its standard error, we should have to observe at least sixteen million individuals." If the average number of offspring per individual is two, for a population at constant size, this is expected to be Poisson distributed with a variance (σ2) of two.
Standard Error = [math]\frac{\sigma}{\sqrt{n}} = \frac{\sqrt{2}}{\sqrt{8,000,000}} = 0.0005 = 0.001/2[/math]
It is implied that two samples of size n=8,000,000, half with the genotype and half without, would be compared for a total of 16 million.
Paragraph Three
Again, adaptive evolution is expected to be very slow and not observable on a time-scale of human lifetimes (however, today we know of exceptions to this where observable evolution can happen quite rapidly). Except, Haldane says, possibly in cases of adapting to changes in the environment many of which are human caused, "agriculture, fishing and industry". "The balance of nature has recently been upset in a manner probably without precedent in our planet's history; and hence on the Darwinian theory we should expect that evolution was proceeding with extreme and abnormal speed."
Page 338
Paragraph Four
The observation is made that in spite of selection against less fit (mutant) individuals in a species, and that this reduction in fitness is heritable, these individuals continue to appear at a roughly constant frequency over time, implying a deleterious-mutation-purifying-selection equilibrium.
Paragraph Five
Two different ways of thinking about fitness are defined, within a generation and over time. To be continued ...
Terms
- Facies - appearance. https://en.wiktionary.org/wiki/facies
