Related Questions
- From evolution, do humans still retain the (now probably unconscious) ability to detect pheremones and learn things
- Do you all believe that the world began with the big bang?
- How did the first ever sheep/cow/goat/kangaroo/wombat/rabbit get on the Earth? or well... be brought onto the Earth?
- Are any of you religious in any way, and if so how does that work with your view on evolution and the origin of life
That’s a tricky question. I guess the best way to answer that question is to talk about how evolution occurs.
Imagine a big herd of giraffes. Over many years, the giraffes will breed with each other and the number of giraffes in the herd will increase. But, the number can’t keep increasing forever. Eventually they might run out of food or space or a pride of lions might move in next door and eat some of the giraffes.
This means not all the giraffes will survive and breed. Some might starve, some might lose fights with other giraffes for space and have to leave the herd, and some will be eaten by lions. But which giraffes will survive and breed, and which ones won’t?
All the giraffes are naturally slightly different. For example, if there wasn’t enough food or everyone, the giraffes with longer necks that could reach the top leaves on the trees survived and bred, while giraffes with shorter necks might have starved. The longer-necked giraffes would survive and breed and produce babies with long necks too. Over many years, the herd contains more and more giraffes with longer necks because they have an advantage when finding food. This change over time is called evolution.
This process of change over time (evolution) can occur at all levels of the food chain, even in single-celled organisms like bacteria and in non-living things like viruses.
For evolution to occur, there needs to be a selective pressure (such as not enough space or food, or a predator), variation within the population (small differences between individuals) and these variations need to be heritable (e.g. if a giraffe has a long neck, it’s babies might inherit a long neck too). Evolution would have started when all of these three things were present, which was probably pretty soon after the first life form appeared.
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I guess nothing really started it. It happens because it does – if something is able to replicate itself, then it will continue to exist in large numbers. If there are lots of things replicating, then some will win out and others won’t.
I am interested in molecules that can produce more of themselves. There is a little molecule – about the size of the molecule in aspirin – that can reproduce itself under the right conditions. You cook up A and B and you get this molecule C. But if you add in C at the start, A and B combine together really fast to produce more C. C accelerates its own formation. Woah! A molecule that forms itself.
There are a small number of examples of this. Some bits of DNA can make other bits combine together. So what you do is you set up some of these molecules in competition with each other, to see which ones win out. And some molecules are better than others. So they “win” by producing more of themselves. We can see this in action with molecules – sorry, you won’t be able to read this, but here’s an example of an article written by a scientist who’s shown this in action: http://www.sciencemag.org/content/323/5918/1229.abstract. If your teacher wants to read this, or if you want a copy, let me know.
So you then ask “what started this off”? Well, it started because the molecule was able to do it. The molecule can evolve because it can replicate itself.
The same applies to creatures – animals of all kinds. They reproduce, and their kids are a bit like them.
I think the answer to your question, then, is that evolution started with molecules that could replicate. Over time, the molecules became people. But that took quite a long time…
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Doe you mean how do a group of animals change their characteristics over time? A classic example is the Peppered Moth in Britain. Hundreds of years ago, most Peppered Moths were light-coloured. As you know, we are slightly different from our parents, so every group of baby moths (caterpillars) had a mixture of light- and dark-coloured moths. Then there were some cities which had lots of pollution, which had black soot on buildings and so on. The light-coloured moths were easily seen by birds and eaten. Dark-coloured Peppered Moths were uncommon, but more and more of them survived, so the next generation of moths came more from dark-coloured moths, and over time the whole population become mainly dark coloured. In recent years, pollution has been cleaned up, and those cities are getting more and more light-coloured Peppered Moths again.
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I don’t know what started it all but I’m very grateful for it because I wouldn’t be here today if it hadn’t.
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