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It is generally believed that the time over which speciation occurs is too short (~10,000-100,000 years) for our museum collections to include many transitional forms between species. (Transitional species between groups are common, but transitional forms between species are not.)

However, more fossils are being discovered over time, and if it is simply a matter of transitional forms being relatively uncommon, we could imagine that at some point in the distant future it will be the rule to have them, rather than the exception.

On the other hand, fossils tend to be associated with areas (like bogs) which are particularly prone to forming fossils. Bogs form in specific areas and exist for limited spans of time, and sample natural history unevenly. If the main limitation on the fossil record is the sporadic formation of fossils, rather than the sporadic discovery of those fossils, then we may never have a full account of transitional forms.

Can we expect to eventually have most of the "missing links?"

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the problem isn't having transitional forms, all forms are transitional, it is recognizing transitional forms, species an all but pointless definition when including time. Fossils are defined by morphology which would be the same for hundreds of related species or distinct to below the species level depending on the organism. When you include time and fossils the common definition of species is meaningless. so looking for species level change is all but impossible simply because there is no way to tell what is what we would call a species in the living population sense.

That said there are fossil lake beds with millions of generations for all but continuously sampling. Lake Malawi being a famous one. What we see is neither classical punctuated equilibrium nor classical gradualism covers the sheer range of speciation events and speeds.

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  • $\begingroup$ I like your answer, but I think you're putting the cart before the horse: just finding enough fossils is already enormously difficult, never mind arguing over transitional forms or different species. I'm reminded of a U. Chicago talk by an evolutionary biologist who tracked the development of whorls in a particular snail over millions of years. It nearly came to blows when a rival group claimed his thesis baseless as there weren't nearly enough fossils in his study to be statistically relevant, despite his exhaustive fieldwork. $\endgroup$ Apr 11 at 2:18
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Your paragraph about fossils of land dwelling animals tending to be associated with bogs fairly well sums up the situation.

Consider the contemporary situation in the remaining wilderness areas of the world. What opportunities are there for future fossils to form? It's no different to how things were thousands and millions of years ago. Some animals will die and their remains will be preserved, other animals will have their remains scattered and even destroyed by predators and other forces.

As now, in the past there were a small number of locations amenable to the preservation of animal remains which resulted in fossils. Fossils examples of every life form that have existed will not be found for this reason.

It's a matter of chance, which animals get fossilized. It's also a matter of chance which fossil sites get preserved and which ones get destroyed by geological forces, such as faulting, earth movements, land subduction, reburial, plate tectonics, etc. It's also a matter of chance which fossils from a fossil site are uncovered. It's also a matter of chance will fossils get identified correctly.

The discovery of past life forms via fossil discovery is largely a process of serendipity. It's a scientific form of lucky dip.

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