Inbreeding and Mother Nature
Natural selection occurs when individuals with certain genotypes are more likely than individuals with other genotypes to survive and reproduce, and thus to pass on their alleles to the next generation.
The reasons for rejecting Darwin's proposal were many, but first of all that many innovations cannot possibly come into existence through accumulation of many small steps, and even if they can, natural selection cannot accomplish it, because incipient and intermediate stages are not advantageous.
There is no strong opinion in evolutionary biology that complexity increase has evolved in living systems by way of natural selection.
It can weed out some of the complexity and so slow down the information decay that results in speciation. It may have a stabilizing effect, but it does not promote speciation. It is not a creative force as many people have suggested.
Selective breeding (also called artificial selection) is the process by which humans use animal breeding and plant breeding to selectively develop particular phenotypic traits (characteristics) by choosing which typically animal or plant males and females will sexually reproduce and have offspring together.
The Darwin & Wedgwood inbreeding tree
I very much fear that my eldest girl Etty will never be strong; and Lenny has been often ailing for last 2 years with intermittent (but only symptomatically so) pulse. My poor constitution like everything else is transmitted by inheritance.
Charles Darwin's studies of heredity, adaptation and evolution included many experiments into the effects of crossbreeding and inbreeding in both plants and animals. Such consanguineous pairing often resulted in weaker, more sickly descendants. Ironically, his own lineage and marriage could have been experiments as well. At the age of 29, he proposed to his first cousin, Emma Wedgwood, the daughter of his mother's brother. Darwin realized the dangers of inbreeding and wondered if his close genetic relation to his wife had had an ill impact on his children's health, three (of 10) of whom died before the age of 11. In a letter to friend, Darwin noted his concern for his children, writing that "they are not very robust."
We have seen that man by selection can certainly produce great results, and can adapt organic beings to his own uses, through the accumulation of slight but useful variations, given to him by the hand of Nature. But Natural Selection, we shall hereafter see, is a power incessantly ready for action, and is as immeasurably superior to man's feeble efforts, as the works of Nature are to those of Art. ... Nature, if I may be allowed to personify the natural preservation or survival of the fittest, cares nothing for appearances, except in so far as they are useful to any being. She can act on every internal organ, on every shade of constitutional difference, on the whole machinery of life. Man selects only for his own good; Nature only for that of the being which she tends. Every selected character is fully exercised by her, as is implied by the fact of their selection.
Nature ... chooses her vocalists from more humble performers than in Europe. ... I do not think Nature ever made a more solitary, desolate pile of rock. ... I do not know of any other instance where dame Nature appears so wilfully cruel. ... Nature herself performs the task of bisection. ... The land is one great wild, untidy, luxuriant hothouse, made by Nature for herself. ... Both are temples filled with the varied productions of the God of Nature.
I had hoped for the credit of Dame Nature. ... What a book a devil's chaplain might write on the clumsy, wasteful, blundering, low, and horribly cruel works of nature! ... Natural Selection is a metaphorical expression of it, and to a certain degree indirect and incorrect, since, even personifying Nature, she does not so much select special variations as exterminate the most unfavourable ones.
What a book a Devil's chaplain might write on the clumsy, wasteful, blundering low & horridly cruel works of nature!