Somewhere along the line, the ancient evergreens - the conifers - lost out to the flowering plants that evolved later and more diversely. Why did they run out of steam? The extent of biodiversity on our planet is a question that's occupied the mindsof evolutionary biologists and taxonomists a lot over the past half century. It has become clear that we won't even have time to find, describe and classify many species before they become extinct. Estimating how many species might currently exist - somewhere between 10 and 100 million - and comparing this with the total number of species so far described (about one and a half million) is largely an exercise in quantifying what we can never know.
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