Evolutionary clock

It is now time to start the evolutionary clock running. To create a new generation of individuals, selections are made from among the members of the present population, copying chosen members one by one into a new population. Survival of the fittest dictates that, in selecting individuals to form part of the next generation, we should choose preferentially the better solutions. Members from the first population which are picked to be placed into the next one are parents their progeny are referred to as children. 

Molecular Clock Places timescales on evolutionary events. See Zuckerkandl, E., On the molecular evolutionary clock, J. Mol. Evol. 26, 34-46, 1987 Easteal, S., A... 

Thus, Wilson and colleagues (see White et al., 1977 Wilson et al., 1977) were led to propose Model II (referred to as Model I by Prager and Wilson, 1988), the essential feature of which is that the a-lactalbu-min-lysozyme duplication occurred long before the mammary gland evolved and before the above repdlian split. They believed that this model was in accord with the known sequence resemblances, did not need to invoke rate acceleration, and was, therefore, consistent with the molecular evolutionary clock. 

Since PCR has been applied to aDNA investigations, the molecular paleontologists have extracted DNA fragments from a wide variety of fossils, artifacts, and museum specimens. For example, DNA sequences have been isolated from such disparate sources as amber-embedded insects (over 100 million years old), fossil herbarium specimens (millions of years old), and Egyptian mummies (over 6000 years old). Comparisons of these and other DNA sequences to those of modem species have provided important information concerning how populations change over time and how much time has elapsed since species shared a common ancestor (i.e., the evolutionary clock). 

Morgan, G.M., Emile Zuckerkandl, Linus Pauling, and the molecular evolutionary clock 1959-1965,/. Hist. Biol, 31, 155-178, 1998. 

Photo 33 Linus Pauling with Dr. Emile Zuckerkandl (right), at an award ceremony in Japan, in 1983. Zuckerkandl co-authored papers with Pauling on molecular evolution and evolutionary clocks (SP 119, SP 120, SP 121). 

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