Left-handed people

[Azathoth]

I think something with like left-handedness, a genetic trait shared by one tenth of the population, it would be acceptable to assume that it was present in EB's timeframe.

There's actually an interesting trend in human left-handedness. Apparently, when the species first appeared, 150000-200000 years ago, let's say, half the population was left handed. Nowadays, supposedly 1 in 20 are left-handed.