Most Dreaded Terror 2 speciation
https://www.youtube.com/watch?v=hVATVF-816U
It is the 19th of February 2018 and I am excited to be explaining something that has been doing us harm for such a long time I scarcely believe it: the mechanism by which inbreeding kills babies and the same mechanism harms us in other ways.
Last lesson (the first lesson) explained that inbreeding does not do its harm by the effect of genes. Were that the case, it would be no great problem. It is Something Else that is inherited but is not genes. And that Something Else is the mechanism that is the point of this whole series. I shall attempt to keep this light because you will need all the cheer and courage you have to see it through and understand it.
A
The niche, sort of like a crude house here, provides the animal with food, shelter, air, water and whatever else it need to survive and reproduce. This is not an individual animal but a population that mate each other and carry on generation after generation. There will be variation within the population – mutations and so forth. The variant may nudge the animal toward the niche or in some other direction. It is inefficient, but over time the animal population is pushed toward the niche. This is called selection.
A A
A A
The first that gets there has an advantage. So SELECTION IS A RACE.
A A A
Now the black A animal can compete for the new niche while the purple A animal stays in the old niche. In fact the black A may get a bit of a boost because, its old niche being filled, it is not held back by selection in that direction, while the orange A animal is drawn in the direction of the new niche as well as the one it already occupied. So SPECIATION IS A RACE. Of course the animal does not knowingly exert itself in this race. Being around animals one notices them engaged in goal oriented, purposeful, conscious, strenuous behavior. But in this race there is no conscious strategy.
https://www.google.com/search?hl=en&biw=1144&bih=550&tbm=isch&sa=1&ei=Hdw2Wu_jFsTIjwScv6zAAw&q=valley&oq=valey&gs_l=psy-ab.1.0.0i10k1j0l7j0i10k1l2.11692.16109.0.18725.4.4.0.0.0.0.87.326.4.4.0....0...1c.1.64.psy-ab..0.4.322...0i67k1.0.u82qJtoRNMI#imgrc=czQxN7dAhVhxGM: downloaded 12/17/17
An animal roams the valley and finds it an adequate niche. There are two individual animals in the population that are siblings, as closely related as they can be, a and a’. One goes across to the far side of the valley. Then it gets cold, and a glacier forms, splitting the valley. The animals cannot cross the glacier.
Two thousand generations pass. In that time speciation has developed. The descendants are a and a’, which are now different species. If the glacier melts, they cannot mate and have fertile offspring.
The population rises to well over a thousand. a and a’can get to each other, but that is not likely to happen right away. As you know in humans there are 46 chromosomes, the parts of the cell involved in speciation, of which 22 pairs are autosomes, structurally the same. For a chromosome from a to wind up in the same animal as a chromosome from a’ will take more than 2,000 generations. By then the descendants are a and a’ which are different species. They cannot have fertile offspring. Since this is true of every member of the population, the whole population dies out.
There are going to be more clues. If you want to cut to chase, go to nobabies.net and read the summaries, the papers and dig into the “source code” postings.