Evolution of dating

Lahn offers an analogy: Medieval monks would copy manuscripts and each copy would inevitably contain errors — accidental mutations.Years later, a ruler declares one of those copies the definitive manuscript, and a rush is on to make many copies of that version — so whatever changes from the original are in this presumed important copy become widely disseminated.

They were less common in sub-Saharan African populations, for example.

That does not mean one population is smarter than another, Lahn and other scientists stressed, noting that numerous other genes are key to brain development.

Fungal fossils do not become common and uncontroversial until the early Devonian (416–359.2 Ma), when they are abundant in the Rhynie chert, mostly as Zygomycota and Chytridiomycota.

Rare in the fossil record are the homobasidiomycetes (a taxon roughly equivalent to the mushroom-producing species of the agaricomycetes).

Francis Collins, director of the National Human Genome Research Institute.

Aside from not knowing what the gene variants actually do, no one knows how precise the model Lahn used to date them is, Collins added.

65 million years ago, immediately after the Cretaceous-Permian extinction that famously killed off most dinosaurs, there is a dramatic increase in evidence of fungi, apparently the death of most plant and animal species leading to a huge fungal bloom like "a massive compost heap".

So suggests new research that tracked changes in two genes thought to help regulate brain growth, changes that appeared well after the rise of modern humans 200,000 years ago.

Since the fungi form a sister group to the animals, the two lineages must have diverged before the first animal lineages, which are known from fossils as early as the Ediacaran.

In contrast to plants and animals, the early fossil record of the fungi is meager.

Two amber-preserved specimens provide evidence that the earliest known mushroom-forming fungi (the extinct species Archaeomarasmius legletti) appeared during the mid-Cretaceous, 90 Ma.

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