Posts Tagged ‘Natural selection’

Humans may have started selective breeding 50-60,000 years ago

November 25, 2012

Humans probably started selective breeding – artificial selection – with the domestication of the dog. Dogs diverged from wolves about 100,000 years ago. The earliest skeletal association of wolves with humans is also from about 100,000 years ago. The earliest evidence of an ancestral dog  is from about 32,000 years ago.

It is not implausible that the first exercise of artificial selection is connected with the domestication of the dog and happened 50- 60,000 years ago.

Ancient dog domestication was the start of artificial selection by humans

“Selection” lies in the begetting and evolution is just a result

November 19, 2012

Recently I posted about two  papers by Gerald Crabtree who suggested that perhaps human intelligence peaked as hunter-gatherers, and

“that we are losing our intellectual and emotional capabilities because the intricate web of genes endowing us with our brain power is particularly susceptible to mutations and that these mutations are not being selected against in our modern society”.

Apparently it is not politically correct to suggest that humanity might be on a “degenerative” evolutionary path for intelligence and Crabtree’s speculations have been the subject of indignant criticism:

Why Gerald Crabtree’s speculations about declining human intelligence are wrong: ….  But like Sanford, Crabtree fails to analyse the problem correctly. In particular, neither show any understanding of quantitative genetics (this is the area of genetics that deals with lots of genes acting on a trait). But unlike young earth creationist Sanford, Crabtree doesn’t even bother to present any data to indicate that an intellectual decline has actually happened.

Discussions and arguments about “intelligence and race” or the “future evolution of intelligence”  or “what intelligence is” or whether “intelligence is selected by natural selection” are fascinating but – in evolutionary terms – are largely irrelevant. Evolution is not a force of change. It is the consequences of a response to change, a result – a report-card of what has happened before.

What counts for evolution – both for what has happened before and for what will happen in the future –  is which inheritable traits lead to the most begetting. It is in the begetting of offspring that all “selection” lies. This applies both with natural and with artificial selection. All other traits which happen to be present in the individual organisms being reproduced and which are inheritable are only carried along with the ride.

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What is evolutionary selection now selecting for?

November 14, 2012

What are the genetic characteristics that are effectively being “selected for” today?

Evolutionary selection is a result not a cause. It is a result describing the genetic change of a population not of an individual. But all genetic change in a population comes about only through the procreation of new generations of individuals.

Evolution then is the result of the survival, success and reproduction of organisms within an environment which is changing. By environment I mean all surrounding factors whether geologic or climatic or of competition within the species or with other species. In a population of organisms the relative success of and subsequent reproduction of those better suited to the environment begets a gradual change in the  characteristics of the surviving organisms.  It is because of the environmental changes in the first place that there is a subsequent change in the characteristics of the organism best suited to that environment. It is this gradual change of the surviving characteristics that we call evolution and we say that the resultant, surviving characteristics have been “selected for”. If the environment did not change and if an organism was suited to its environment, the genetic make-up of the organisation would always tend back to its stable equilibrium position. Any mutational changes would provide no benefit and would just die away. Without environmental change there would be no evolution to report. Over long stretches of time and many thousands of generations, these gradual changes of environment have been sufficient to have created all the species of living things that have ever existed and to have eliminated all the non-viable species that have gone extinct.

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