Biology - Evolution

Darwin and the Theory of Evolution Explained Simply

In the 19th century, Charles Darwin described how living things change over very long time spans and how new species arise. The core mechanism behind it is called natural selection.

Variation + Selection + Heredity = Evolution random differences between individuals, a survival advantage from those differences, and passing them on to offspring
early form present-day form

The size of the circles here stands for small changes accumulated over very many generations - not for a single big leap.

đź’¬ Mia asks Grandpa Theo

Mia

Does "survival of the fittest" mean the strongest animals always win?

Grandpa Theo

No, that's a big misunderstanding! It actually means "best adapted" - not strongest. A moth that's well camouflaged in the dark beats its predators not by fighting, but simply by being overlooked.

Mia

But where do the differences between animals even come from?

Grandpa Theo

Through random small changes in the genetic code, called mutations. Most don't matter, some are harmful - but sometimes one happens to be useful. Animals with the useful trait tend to have more surviving offspring on average, so the trait becomes more common in the population.

Mia

And eventually that turns into a whole new species?

Grandpa Theo

When two groups of a species develop separately for long enough - say, on different islands - enough small differences can pile up that they eventually can't reproduce with each other anymore. At that point they've become two separate species. That's exactly what Darwin observed in the finches on the Galápagos Islands.

Not just the past

Evolution is still measurable today: bacteria develop resistance to antibiotics within just a few years, because resistant bacteria survive and reproduce - an example of natural selection happening in real time.

Important: evolution has no goal and no "drive" toward perfection - it's simply the result of randomly useful traits spreading through a population.

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