Interesting stuff about the science of evolution and the natural world

Posts tagged ‘darwin’

Family tree – literally

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Researching family history is very popular these days. With a bit of luck you might be able to go back a few generations and maybe find out who your four times great grandparents were and what they did. Going back any further begins to get a bit tricky, but I guess it’s possible to indulge in a bit of imagination. We could think of our ancestors from a thousand years ago working the land to put food on the table, or from 20,000 years ago, before farming, living as hunter gatherers with very simple tools. At around 100,000 years ago, our ancestors are a relatively small population existing only in Africa, and amongst them will be our approximately 5,000 times grandparents.

Now we get to the bit that needs the mind to take a slightly bigger leap in imagination. If we could find our 250,000 times grandparents they would be apes, also living in Africa, some 6 million years ago. OK, granted this is nothing new – ever since the famous cartoon of the head of Darwin on the body of an ape, from 1871 – but it’s quite sobering to remind ourselves of the closeness we share with the rest of the natural world, and the fact that we are not so different from other animals.

So we can keep going back through our direct ancestors – to a primitive primate, then the first shrew-like mammal, an early reptile (or synapsid, to be correct), the first land vertebrate, a fish, a marine worm, a very simple multicellular animal, a single celled animal and right back to bacteria.

But with ancestry, you’re not restricted to direct ancestors, you could also consider other branches to your family tree – your cousins. First cousins share the same grandparents, second cousins great grandparents, and so on. Using these links we can begin to find our relationships to other animals not within our direct ancestry. But now comes the bit that gets a bit more weird, to me anyway, but still doesn’t cross the line into fiction. If we go back to a linking ancestor way back in the time of single celled life and follow a different lineage to the present we would find that, for example, our cousin was an oak tree – in fact all oak trees and all plants. It’s impossible to know the correct numbers but I guess it could be something like a 100 billionth cousin many million times removed. And this means an actual cousin, not using it as a metaphor for species evolution. All individual oak trees are our literal cousins, albeit somewhat distant.

I think I have a new found respect for the tree huggers.

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Darwin didn’t discover evolution

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Well it might be a bit of a cliche to bring up the great man in my first post, however it seems as good a place to start as anywhere. But of course Darwin was not the discoverer of evolution. His original idea was the theory of change by natural selection as an explanation of how evolution happens. By amassing such a huge amount of detailed research and explaining every step of his thinking in great detail, he finally put evolution into the minds of the general public and caused a fuss and fascination that continues to this day.

The first ideas about evolution date back even as far as the ancient Greek philosophers. There were a few suggestions about how animals may have come about and that they might undergo change, but they don’t bear much comparison to modern science. It was not until the 17th and 18th Centuries that some clearer ideas about the gradual change of species began to arise, but an explanation of how it might happen was still elusive. Then in 1809 the Frenchman Jean-Baptiste Lamarck put forward one of the most important theories of the time. He considered that characteristics acquired during the lifetime of an individual would be passed on to it’s offspring. So, for example, if an animal used a particular muscle to a great extent and built this muscle up very strongly, this larger muscle would then be passed on to the next generation. Modern genetics, of course, tells us this is not true.

Then came Darwin’s Origin of Species, or, to give it it’s full title – On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life – in 1859. Note the lack of the word evolution, and it is a word he uses very few times throughout the book. I don’t know if he did this on purpose, but it does seem a little strange.

Very briefly, his argument was this. He noted that all individuals within a species showed variations from each other. He also noted that there were far more offspring than could possibly survive, and so there would be a struggle for existence. He therefore concluded that those varieties with beneficial traits within a particular environment were more likely to survive and prosper in the population, so giving rise to gradual change and eventual extinction of the less favoured variety. Given enough time and enough generations the changes would be sufficient for a new species to come into being.

There is a beautiful simplicity to the theory, but given the immense amount of time that life has existed, there is also a beautiful complexity and variety to the life forms that we see today as a result of evolution. I’ll leave the last word to the man himself. This is the closing sentence from The Origin of Species, and I find the last word a little ironic.

There is a grandeur in this view of life, with its several powers, having been originally breathed into a few life forms or into one; and that, whilst this planet has gone on cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.

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