How can we say that we are evolving with time
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Answer:
Evolution is one of the greatest theories in all of science. It sets out to explain life: specifically, how the first simple life gave rise to all the huge diversity we see today, from bacteria to oak trees to blue whales.
For scientists, evolution is a fact. We know that life evolved with the same certainty that we know the Earth is roughly spherical, that gravity keeps us on it, and that wasps at a picnic are annoying.
Not that you would know that from the media in some countries, where evolution is ferociously argued about – put down as "just a theory" or dismissed as a flat-out lie.
Why are biologists so certain about this? What is the evidence? The short answer is that there is so much it's hard to know where to start. But here is a very cursory summary of the evidence that life has, indeed, evolved.
It might help to first spell out quickly what Darwin's theory of evolution actually says. Most of us have the general idea: species change over time, only the fittest survive, and somehow a monkey-like creature gave rise to human beings.
It is hard to accept that you are descended, through countless generations, from a worm
Darwin's theory of evolution says that each new organism is subtly different from its parents, and these differences can sometimes help the offspring or impede it. As organisms compete for food and mates, those with the advantageous traits produce more offspring, while those with unhelpful traits may not produce any. So within a given population, advantageous traits become common and unhelpful ones disappear.
Given enough time, these changes mount up and lead to the appearance of new species and new types of organism, one small change at a time. Step by step, worms became fish, fish came onto land and developed four legs, those four-legged animals grew hair and – eventually – some of them started walking around on two legs, called themselves "humans" and discovered evolution.
This can be hard to believe. It's one thing to realise that you are not identical to our parents: perhaps your hair is a different colour, or you are taller, or have a more cheerful nature. But it is much harder to accept that you are descended, through countless generations, from a worm.
Plenty of people certainly don't accept this. But forget all the drama for a moment. Instead, begin as Charles Darwin did: on your doorstep.
Darwin's book On the Origin of Species, first published in 1859, begins by asking the reader to look around at the familiar. Not unexplored tropical islands or faraway jungles, but the farmyard and garden. There, you can easily see that organisms pass on characteristics to their offspring, changing the nature of that organism over time.