[Alter Kaker]

We can use a (purportedly) 50,000 year old horse, if you like.

A 50,000 year old member of the equus genus would likely not have been able to easily breed with a modern horse. Equine evolution has been remarkably well documented.

We group things together according to similarities but the construct is of course, artificial by definition. (e.g. by one standard peanuts are regarded as nuts, but by others they are not nuts).

Huh? Peanuts are not nuts, they are legumes. I don't believe that there is any taxonimical controversy over their classification.

[sittnick]

A 50,000 year old member of the equus genus would likely not have been able to easily breed with a modern horse. Equine evolution has been remarkably well documented.

A 2,000,000 year old modern horse (Equus stenonis) was believed to have been found in Italy.

Huh? Peanuts are not nuts, they are legumes. I don't believe that there is any taxonimical controversy over their classification.

The world is a lot bigger than taxonomy, which is a man-made construct. Nutritionally they are regarded as nuts, and are nutritionally classified in the meat group. Taxonomical categorization is only ONE way of thousands to categorize things. It is often impractical and dopey to insist on taxonomical classification, which is why a jar of mixed nuts can be up to 50% peanuts. If your grocery store put the Planters' peanuts by the lentils, it might be right according to the current system of taxonomy, but it would drive the customers crazy.