the world from beginnings to 4000 bce feb 2008

[...]... passed on from parents to their offspring was enough for their purposes It was only after the birth of the science of genetics at the turn of the twentieth century that explicit discussion of evolutionary mechanisms really took off; but in fact the first principles 4 The World from Beginnings to 4000 bce of genetics had been discovered as early as 1866 in what is now the Czech Republic by the abbot... see in the fossil record is the (dimly reflected) histories of species 12 The World from Beginnings to 4000 bce What seems to happen, then, is that any successful and reasonably widespread species tends to diversify, developing local variants in different parts of its range We routinely see this among species of the order Primates, the grand group of living things to which we belong together with the apes,... offerings to the table The geneticists brought their newfound understanding of the mechanisms by which genes interact in reproducing 6 The World from Beginnings to 4000 bce populations and of how they are passed along and occasionally modified between generations The naturalists brought their expertise in the diversity of nature and in what species were and how new species might be formed And the paleontologists... don’t know exactly what genetic changes were involved in the shift from one body type to 14 The World from Beginnings to 4000 bce the other, but molecular and developmental geneticists are beginning to lift a corner of the curtain that lies over this mystery And in the process they have provided a new set of reasons to revise our understandings of the evolutionary process as a slow, stately progression... unchanged for periods of time that could stretch into the millions of years, and then to disappear with equal suddenness, to be replaced by other species, which might or might not have been their close relatives The gaps in the fossil record, Eldredge 8 The World from Beginnings to 4000 bce and Gould suggested, might not simply reflect a lack of information but, rather, might actually be telling us something... to them, too We tend to take what is familiar for what is natural or for what should be, and there is only one hominid species on Earth today: Homo sapiens Once the evolutionary synthesis had become widely accepted, then, it seemed reasonable to many to assume that the evolutionary story of mankind had consisted of a steady progression from primitiveness toward perfection Indeed, during the 1960s there... natural selection To take the hominid example, it is quite plausible to attribute the apparently rather steady hominid brain-size enlargement that we see in the fossil record to the relative success of larger-brained hominid species in the competition for life rather than to the competitive advantage of larger-brained individuals within each population According to Eldredge and Gould’s theory, then, each... before the publication of Origin of Species in 1859 By permission of the Syndics of Cambridge University Library 16 The World from Beginnings to 4000 bce species that had ultimately gone extinct But nonetheless the linear idea persisted, and some still today defend the notion that there is a ‘‘main line’’ of human descent along which a gradual succession of species can be followed According to this... differ from place to place (for instance, today we have polar bears in the Arctic and giraffes in the African tropics), geologists were rapidly able to piece together a broad picture of Earth’s long history by correlating faunas from one region to another and by observing where they lie in relation to layers not containing fossils This process is still ongoing, of course; but at this stage of the game... Fortunately, the TL method works for the entire period during which ancient humans have been regularly using fire, and it has also been used 22 The World from Beginnings to 4000 bce to date the quartz in sands whose electron traps had been emptied by exposure to sunlight Perhaps the most widely used method of radiometric dating, particularly in older periods and where volcanism was rife, dates not the fossils themselves . y0 w0 h0" alt="" The World from Beginnings to 4000 bce