Having a fuckload of babies certainly ups the chances, mate... ;) On Mon, Dec 29, 2008 at 8:53 PM, chazwin <[email protected]> wrote:
> > > > On Dec 29, 4:45 am, "Chris Jenkins" <[email protected]> > wrote: > > Survival of the fittest is indeed commonly misunderstood, most especially > > when it comes to humans. It's not survival of those most fit to survive. > > It's survival of those most likely to procreate, and so it has been > through > > out all of evolution. > > Actually it is those who are able to produce successful offspring in > their given environment. > Procreation is not enough in itself. > > > And so it is that those with nought else to do but rock the bedposts turn > > out children at three times the rate... ;) > > > > On Sun, Dec 28, 2008 at 11:30 PM, archytas <[email protected]> > wrote: > > > > > The phrase "survival of fittest" is widely misunderstood Many wrongly > > > assume it means that evolution always increases the chances of a > > > species surviving. Evolution sometimes results in individuals or > > > populations becoming less fit and may occasionally even lead to > > > extinction. > > > > > There are several ways in which evolution can reduce the overall > > > fitness of individuals or of populations. For starters, natural > > > selection can take place at different levels - genes, individuals, > > > groups - and what promotes the survival of a gene does not necessarily > > > increase the fitness of the individuals carrying it, or of groups of > > > these individuals. > > > > > For example, parasitic DNA elements, or transposons, can spread > > > through a population even though they make their host organisms less > > > fit. Transposons are one cause of genetic diseases such as > > > haemophilia. > > > > > Similarly, selfish individuals may thrive at the expense of altruistic > > > individuals in a group - making them the "fittest" - even though they > > > make the group as a whole less competitive. Such cheaters can have > > > disastrous consequences. > > > > > In 1932, J. B. S. Haldane suggested this could even lead to the > > > extinction of populations - a phenomenon called evolutionary suicide. > > > Models and some experimental evidence suggest he was right. > > > > > For instance, when nutrients run low, individual myxobacteria (slime > > > bacteria) may come together to form a fruiting body to produce spores. > > > Lab studies have shown that cheating myxobacteria that only produce > > > spores and never help form the non-spore producing parts of the > > > fruiting body can drive populations to extinction. > > > > > Genes capable of driving populations to extinction might have a > > > practical use, however. Biologists are exploring the possibility of > > > releasing engineered parasitic DNA into populations of malaria- > > > carrying mosquitoes. > > > > > There is concern that something similar could happen accidentally. > > > Fish that have been genetically modified to produce a growth hormone > > > grow faster and larger, mature earlier and produce more eggs. But they > > > are less likely to survive in the wild than unmodified fish. According > > > to the Trojan gene hypothesis, a gene variant that produces such > > > characteristics could spread rapidly through a wild population despite > > > reducing individual fitness, and eventually drive the population to > > > extinction. > > > > > Another way in which evolution can reduce a species' chances of > > > survival is through the accumulation of detrimental mutations. > > > Mutations provide the vital raw material for natural selection, so if > > > the mutation rate is too low a population will not be able to evolve > > > fast enough to keep up with environmental changes. > > > > > If, on the other hand, a population's mutation rate is too high, > > > detrimental mutations may accumulate faster than natural selection can > > > eliminate them. Eventually, the number of mutations can exceed the > > > "error catastrophe threshold", again leading to the extinction of a > > > population. > > > > > In theory, any species with a very small population could accumulate > > > deleterious mutations faster than it can eliminate them. The problem > > > is especially severe for asexual organisms such as the Amazon molly - > > > an effect known as Muller's rachet. > > > > > It is far less of a problem for sexually reproducing species because > > > the exchange of genetic material between chromosomes can separate good > > > and bad mutations. Some unlucky offspring get saddled with lots of > > > nasty mutations and die out, while the lucky ones get hardly any. > > > > > In theory, a mutation catastrophe can also occur as a result of > > > linkage. This refers to gene variants that are inherited together > > > because they sit next to each other on a chromosome. Suppose a > > > mutation that greatly increases the mutation rate somehow ends up next > > > to a new mutation that greatly increases fitness. The immediate > > > fitness benefits of the beneficial mutation will initially mask the > > > deleterious effects of the "mutator" mutation, meaning both mutations > > > will rapidly sweep through a population, ultimately with disastrous > > > consequences. > > > > > A few doctors hope to exploit mutation accumulation to treat diseases. > > > Certain viruses such as HIV are already close to the error catastrophe > > > threshold. Drugs that increase the mutation rate of the viruses still > > > further might push them over the threshold and drive a population of > > > viruses inside a person's body to extinction. > > > > > Finallly, it has long been recognised that the competition between > > > members of the same species to reproduce - sexual selection - can > > > favour traits that reduce a species' overall fitness. Male peacocks > > > with the biggest and brightest tails might get the females' attention, > > > but lugging around a heavy, conspicuous tail reduces their chances of > > > survival. > > > > > Studies of threatened bird species suggest that sexual selection can > > > indeed drive populations to extinction. Some biologists go so far as > > > to blame sexual selection for the conspicuous consumption that > > > threatens humanity's future. > > > > > According to the handicap principle, features such as peacocks' tails > > > evolve precisely because they are disadvantageous. Consider an > > > individual who is trying to signal to females how fit and strong he > > > is. If the signal is easy to make, weaker males can easily cheat by > > > making the same signal. But if making the signal is costly - such as > > > growing a large, clumsy tail or giving away food - there's no way to > > > cheat. > > > > > Proving that any of these phenomena have ever led to extinctions in > > > the wild is far from easy, because any species to which this has > > > happened are, of course, no longer around to study. The indirect > > > evidence is growing ever stronger, though. > > > > > The above is from this week's New Scientist. I've come across about > > > 20 misconceptions of evolution reading literature recently and, of > > > course, creationist myths are legion. My interest is indirect - I'm > > > looking for examples of why our debates are so little evidence based > > > for a theory of language. > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups ""Minds Eye"" group. 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