Wouldn’t species always be evolving? Example: Why do we find a couple of dozen T-Rex skeletons and not all the evolving stages that lead to the T. Rex over millions of years? And are those specimens classified as different species?
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It is, and we do find them all the time. We don’t have fossils of every single creature that ever lived because fossils are very hard to form. They only form under very specific conditions. For example, we have only ever found 13 Archaeopteryx fossils, but there were probably more than 13 Archaeopteryx ever in history.
The T-rex evolved from older and smaller theropods. We do have fossils of them, but with just a few examples it can sometimes be hard to tell what’s a different species and what’s just a juvenile or regional variation.
More generally, evolution happens in quick bursts and slow crawls. When the environment is stable for long periods you often don’t see dramatic changes to the animals occupying various ecological roles. You get smaller tweaks that are hard to parse from fossils.
You get dramatic changes only when the environment itself changes. Mammals stuck to the same set of squirrely body plans for a hundred million years to stay out of the dinosaurs’ way.
Then one day the dinosaurs were gone, and mammal evolution exploded to fill all the vacancies.
It is actually very rare for something to fossilize. Even more rare for small animals to fossilize. The bones and impressions we do have are just a tiny window into the history of the earth. The farther back you go, the luckier you’ll be to find anything
Well yes, because they are all always evolving, every species is “transitional”, there isn’t really a “final form”. It’s not DBZ (though DBZ can’t seem to settle on s final form ever either lol). We find fossils that are similar enough => same species, if they’re differemt enough (based solely on petrified bones need I remind) => different species. We don’t actually have a way to make fossils fuck each other and then have their kids fuck each other too, so as to confirm that they are, in fact, of a single species, by the scientific definition.
Every fossil is a fossil of a transitional animal, between the organism from which the fossil evolved and the fossil into which it was evolving. It’s just that so very few animals actually go on to become fossils after they die (everything needs to go just right for it to happen), there are a great many additional transitional species that aren’t memorialized in the fossil record.
it is.
evolution is a gradual continuous process so every fossil is transitional
every single one
Every fossil we find is, in effect, a transitional fossil. Evolution takes such immense amounts of time that any changes in a particular generation or indeed multiple generations are likely to be so slight as to be very difficult to recognize.
Just consider the analogy of the creation of the Atlantic Ocean. The North American and European plates are moving apart by about 2.5cm each year. In a long human life your talking about maybe a 2 meter change. Well the Atlantic is around 4,800,000 meters wide. Over hundreds of millions of years you get movement over vast distances but any snapshot of time isn’t going to really show you anything. It’s the same principle with fossils.
I think this used to be explained by punctuated equilibrium, which is possibly true in some cases, but as others have said, there are transitional forms.
Every fossil is a transitional fossil. Every living being is an intermediary step in it’s species evolution. The changes can be subtle enough that they are barely noticeable between one generation and the next because it can take many generations over millions of years to see actual structural or anatomical changes that are visible at a macro level
The fossil record only occurs if the ground is suitable to transforming creatures into fossils, which is quite rare. The vast majority of things that die will not fossilize, and the tiny minority that does is spread out over our entire planet and in many different rock layers. It is possible that we will fill in many of these gaps in the coming centuries, but even so, it’s likely that most gaps will remain. Likewise, many fossils that once were have likely been destroyed by compression or melting of the rock layers they were in.
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