| Journal Language Quiz Calendar |
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Duplication and ET |
Wed 25 Jan 2006 12:00AM compton |
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A friend of mine recently said that watching kids is fascinating because you can see how they copy each other, and that copying is at the heart of learning. It appears to be a basic element of human nature - if we hear a sound, such as a car engine or a strange animal cry, we can often do a reasonable attempt at duplicating it with our own voice. Babies and children learn language and behaviour in large part by copying what they've witnessed others say and do in similar situations.
Copying also figures on lower, more physical levels, closer to the everyday 'hardware' of life, where individual cells split to make duplicates of themselves during the natural process of growth. On a molecular scale, a cell is a massive entity, and is itself composed of smaller individual units with their own functions. The cell's nucleus is considered the control centre and is where the precious DNA is located. DNA, although tiny compared to the cell, is itself a huge molecule. In human cells, 26 (I think) molecules of DNA form our genetic signature - these are the chromosomes, and when a cell splits, replicating itself, each of these are duplicated. The process of DNA replication is an insanely complicated orchestra of which my understanding is limited. I believe it is led by smaller molecules, such as RNA, which help split and recombine the strands of the famous double helix of DNA. It is this very ability of DNA to duplicate itself under natural conditions (in the presence of other substances) that links it inextricably with life. As copies are made, errors can and do happen - the DNA is not copied correctly. By accident a new type of cell can be made, perhaps one that works better in conjunction with others like itself. Cells like this would tend to be found clumped together, continuing to duplicate in their new form, with further happy accidents resulting in increasingly complex, but workable, systems. Right now of course, the planet is populated by a staggering number of animal species, from whales to mice, ostriches to people. Animals are, of course, mind-bendingly head-poppingly complex systems, which function quite naturally and easily in the natural conditions of the planet. These systems can only plausibly be created in nature by this repeated but slightly error-prone cellular copying. Of course, a human-like God could come down and create people and animals directly from mud and dust, but that's a whole nother theory that is best discussed elsewhere. Anyway, the point I'm trying to make is that it is the property of slightly flawed self-duplication that underpins what we know as life. When looking for life on other planets, scientists focus on planets that have similar conditions to Earth's, apparently working from the assumption that DNA et al are the only molecules capable of nearly-but-not-quite-perfect self-replication. It strikes me that a more wide-ranging approach would be to begin with the study of what is involved in order for molecules to be self-replicating, along with what environmental conditions would be required for the various possibilities. For instance, some molecules are only formed under high pressures at really high temperatures. Could any of these molecules be self-replicating, and if so, could a planet, or other astronomical body, offer these conditions and the elements required to build the molecules? |
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compton1:07 am, Saturday, 2 August 08 |
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Sex differentiation would appear to have happened in this order: asexual:- each organism reproduces itself i.e. all female hermaphrodite:- at first (asexual plus ability to conceive and ability to impregnate) sexual:- only after a hermaphrodite stage could evolution arrive at modern day reproductive behaviour as in mammals. Moving from asexual to hermaphrodite reproduction seems conceivable to my layman's understanding. Very early on in life's story, asexual uni-cellular organisms could have developed an ability to merge their DNA somehow, such that offspring had two distinct sets of chromosomes. However it happened, this hermaphrodite sexual reproduction must have evolved very early on, and the low level mechanism for this chromosome exchange must have been preserved from then on. (but possibly lost in some species that revert to hermaphrodite reproduction). Is there a clear transition from hermaphrodite to sexual? First you need a class of organism that can no longer reproduce, that can no longer produce its own eggs, but can only impregnate: the first male. Its survival as a separate sex then depends on its genetic blueprint recurring in its offspring Most if not all animals have a twin set of chromosomes. This allows a sort of error checking, but could it also suggest a possible origin in merging of two whole cells? What are known as 'gametes' - male and female 'half' cells prior to conception - are the vestigal but essential remnants of our first, unicellular ancestors to reproduce sexually. Each gamete has one of its parent's sets of chromosomes. Some of these chromosome sets could be thought of as deformed, having a malformed X chromosome that resembles a Y. By this interpretation, animals whose DNA has two well-formed X chromosomes are the more 'original' form of the organism; XX is the female. Because the female always has two X chromosomes, and offspring get one chromosome from the mother and one from the father, offspring can only ever have XX or XY pairs (no YY). So you could well imagine single-sex hermaphrodite animals with both reproductive and impregnative (probably an actual word for that..) organs existing initially, with a 'malformed' X appearing at some point - malformed in some critical, crucial and persistent way that results in the loss of 'womb' function but retains the ability to impregnate others. This is the first male, and because it then creates that XX / XY thing, it persists in the gene pool. This two sex arrangement clearly has significant evolutionary advantages - ie the ability to change the species rapidly (but in a very directed way) towards greater organisational complexity. It's the evolutionary engine that created the higher life forms like us as well as all the other animals. |
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Yuan6:31 am, Monday, 20 February 12 |
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| I don't think anyone's arguing that languages are transmitted genetically. Languages being transmitted by fathers is definitely cultural and fathers being more dominant is certainly something which needs to be considered. | |
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/xkcd/ Felidae
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