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quote:Originally posted by neilepI thought it was generally considered that Dino died out due to a cataclysmic collision or some Earthbound disaster....personally I just think they upped and went off planet hopping !
quote:Originally posted by DoctorBeaverI agree; although how long would a species need to survive before being labelled as successful? There was a lot of evolution involved with dinosaurs - and they were around for a very long time - but ultimately they failed.
quote:The process of evolution can be summarized in three sentences: Genes mutate. [gene: a hereditary unit] Individuals are selected. Populations evolve.
quote:Originally posted by DoctorBeaverGood site about evolutionhttp://www.talkorigins.org/faqs/faq-intro-to-biology.htmlFrom that site:- quote:The process of evolution can be summarized in three sentences: Genes mutate. [gene: a hereditary unit] Individuals are selected. Populations evolve.
quote:Nowadays, the idea of passing on to offspring characteristics that were acquired during an organism's lifetime is called Lamarckian. This view was, until very recently, thought to be completely inconsistent with modern genetics, but recent discoveries, as discussed in the article on epigenetic inheritance, show that this is not quite the case. So Lamarckian ideas continue to be important even when his theories on the general mechanics of evolution were wrong.. Another contemporary view is that memetic ideas of cultural evolution could be considered a form of Lamarckian inheritance of non-genetic traits.
quote:Evolution is not progress. The popular notion that evolution can be represented as a series of improvements from simple cells, through more complex life forms, to humans (the pinnacle of evolution), can be traced to the concept of the scale of nature. This view is incorrect.
quote:The primary line of evidence for this is the similarities between young apes and adult humans. Louis Bolk compiled a list of 25 features shared between adult humans and juvenile apes, including facial morphology, high relative brain weight, absence of brow ridges and cranial crests.
quote:Neoteny in humansThere is a controversial debate which argues that humans are neotenous and retain certain juvenile characteristics into adulthood that are not seen in other great ape species. Many scientists discredit this argument since there is no delay of sexual maturity in humans.While neoteny is not a physical state that humans experience, it is widely acknowledged that paedomorphic characteristics in women are desired by men.
quote: but in one sense one might say that evolution does progress
quote:Originally posted by DoctorBeaverSort of. I noted the bit about earlier generations being re-introduced & taking over from later ones. That means that although it may seem as if evolution is advancing, it is only advancing with regard the immediately predeeding generation; the evolutionary chain as a whole is not.
quote:The point I was making is that subsequent generations, some of which will not be replaced by preceding generations, have the possibility of being more complex than their ancestors. That they have the possibility does not mean they inevitably will be, but it would indicate that on average there would be a progressive increase in complexity.
quote:Originally posted by DoctorBeaverI think, in general, that is probably correct. However, I can think of a few questionable examples. Take the slow worm. That has evolved from a lizard with legs. Seals' flippers are also residual limbs. Are those creatures more, or less, complex than their ancestors?
quote:Originally posted by sharkeyandgeorgemy understanding is that you dont ever lose chromosomes but that they depend on the evolutions of the dna thats why the fern has so many well over a hundred because it has exsisted so long and evolved so much i suspect that apes have more than humans because they had too evolve twice since the splitting of species to take advantage of envioromentle niches where as humans with our supreme adaptability were able to fill similar niches with one body typeGiggidy Giggidy GooThe philosopher Q man
quote:The scientists reported that the banding pattern surrounding the centromere on human chromosome 2 bore a striking resemblance to the telomeres at the ends of two separate chromosomes in chimpanzees and gorillas. They proposed that in the hominid lineage, the ancestral forms of those two chromosomes had fused together to produce one chromosome. The chromosomes weren't lost, just combined. Other researchers followed up on this hypothesis with experiments of their own. In 1991, a team of scientists managed to sequence the genetic material in a small portion of the centromere region of chromosome 2. They found a distinctive stretches of DNA that is common in telomeres, supporting the fusion hypothesis. Since then, scientists have been able to study the chromosome in far more detail, and everything they've found supports the idea that the chromosomes fused. In this 2002 paper, for example, scientists at the Fred Hutchinson Cancer Research Center reported discovering duplicates of DNA from around the fusion site in other chromosomes. Millions of years before chromosome 2 was born, portions of the ancestral chromosomes were accidentally duplicated and then relocated to other places in the genome of our ancestors. And this past April, scientists published the entire sequence of chromosome 2 and were able to pinpoint the vestiges of the centromeres of the ancestral chromosomes--which are similar, as predicted, to the centromeres of the corresponding chromosomes in chimpanzees.
quote:All the great apes, that is both major taxa of Pan, P. paniscus (bonobo) and P. troglodytes (‘common’ chimpanzee) as well as the subspecies of Gorilla and the subspecies of Pongo (orang-utan) have 48 chromosomes whereas we have 46.Applying the simplest principles of parsimony to this observation it would seem fairly obvious that the last common ancestor of the Hominoidae (that is the great apes and the hominids) had 48 chromosomes too. A simple cladogram of this indicates that 48 (often written 2n = 48) chromosomes is the primitive condition and that descended from that ancestor only humans have the derived condition of 46.
aren`t humans nearly at the upper limit of brain size as related to efficiency? much bigger or more convoluted and impulses would start taking longer to arrive at their target neurone, so there`s a certain maximum size for optimal efficiency.
does not our ``evolutionary future`` lie in electronic enhancement and the co-mingling of our organic bodies with artificial computational elements?``cyborg`` is a nasty word. i prefer ``post human``