Do human cells experience natural selection between them and thus experience their own evolution? If the answer is “no,” what are the implications? Does it mean that they have remained the same possibly since the development of multi-cellular organisms? That would seem to me to mean that natural selection evolution has occurred only between the organizing of the cells, in other words, between the multi-cellular organisms. If the answer is “yes,” will give a rough explanation for how that occurs---and how it has affected gross human evolution? It has been a long time since I took biology in college, but I assume your answers will be “no,” not “yes.” If so, does it mean that there is absolutely no natural selection evolution going on between our individual cells or merely that it is of no consequence in explaining the change that has gone on in primate-evolution-to-us? Charles http://atheistic-science
No, they don't. Random mutation and copy errors account for gene variation. Then there is natural selection, gene flow and genetic drift that act on a species genome, hereby favoring different versions of genes in different habitats. All the cells in your body have the same genetic makeup which you inherited from both your parents (plus maybe some mutation). The DNA in your sperm cells contains half your genome and recombines at conception with another genome halve of an egg cell (that of your partner). This makes for a new genome that has it's own unique properties. Now repeat this for lots of generations and you end up with an altered genome. And the genome is the blueprint for your body. Hope this helps Please Register or Log in to view the hidden image!
Thanks! I think I understand that, but how is it that these individual cells can co-exist among each other for extended periods of time without any biological natural selection going on between them? Did the natural selection evolution among cells actually come to an end when life evolved the multi-cellular organism? charles http://atheistic-science.com
Well, the individual cells are now part of a whole that needs to work together in order to survive. So there is no competition. In fact, there is such a thing a programmed cell death. If a cells DNA gets damaged beyond repair (or because of some other threat to the whole) it kills itself in order not to be a thread the whole. This is what goes wrong in cancer.
Actually, I'd say that natural selection is going on between them all the time. The selection, though, in the case of a multi-cellular organism, is for generally for cooperation among cells. Cells that do not work in concert with other cells in the organism are generally attacked and eradicated. That is what happens with foreign bacteria and viruses in the human body, for example. Cancer cells are an exception - they have apparently found ways to propagate themselves, but at the expense of the organism that supports them. They also manage to avoid the body's defences. Multi-cellular life originally evolved when different cells found that they were more successful (in terms of reproduction etc.) working together in symbiosis than in competing with one another. Thus, natural selection actually favoured cooperation in this case. A multi-cellular organism like a human being is, in a sense, the ultimate in cooperation among cells - even to the extent where every cell now shares its DNA with every other cell, so that all survive or fall together, so to speak.
