As is common knowledge, the founder (more-or-less) of modern genetics was Gregor Mendel, who first laid down the laws of Mendelian inheritance. In particular, he discovered the existence of dominant and recessive traits in pea plants, and the re-discovery of his discovery set into motion the modern field.

My question is this: how much was known about human heredity before Mendelian inheritance was discovered? I imagine human beings would have always noticed that children end up looking like their parents. But would they have known the nitty-gritty of it, for example, that black hair was more likely to be passed on to children (a la Game of Thrones), or that two people with cleft chins can still have a cleftless kid? Did any of the ancients or later scientists ever tackle the subject in a significant way?

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    Farmers and Herdsman had been using directed breeding for millennia prior to Mendel. – Oldcat Sep 8 '14 at 19:35
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    Mendel did not study human heredity, he studied plants. This is a question about the evolution of science, not history (human events). You can read the book "Heredity Descent" by Orson Squire Fowler to get a good idea of what constituted scientific genetics before Huge de Vries. de Vries, by the way, is the key figure in knowledge of genetics. Mendel was completely ignored in his own time, so his "discoveries" had no effect on the society. It was only after de Vries published his theories in 1900 that Mendelian inheritance started to be widely understood. – Tyler Durden Sep 8 '14 at 19:39
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    Reading between the lines of the traditional terminology, that "some traits breed true and others skip a generation", it would seem that breeders have known for a long time to not abandon first generation offspring without the desired trait. However, I think that phrase also sums up the complete understanding prior to the recognition of Mendeleev's work. – Pieter Geerkens Sep 8 '14 at 22:40
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    @PieterGeerkens +1 to your comment! However i feel obliged to tell you that Mendel is not short for Mendeleev...that was the chemistry guy. – Matthaeus Sep 10 '14 at 10:59
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    @Matthaeus: Oops! Braun fart there by me; I do know better. – Pieter Geerkens Sep 10 '14 at 22:02

Of course nothing was known specifically about genes, or anything smaller than what people could see (except for some philosophical theories...anatomists etc.).

But mankind made a lot of conscious usage of heredity, especially in selective plant breeding and animal husbandry. Note that most of the grains (wheat, rice...but originally not much more than grass) were hardly digestible before they were bred to be so. Many fruits, like all the different rosaceae (apples, pears...) weren't very tasty, nutritious, big or resistant before mankind saw potential in them; in the latter case we're even talking about the time after the last ice age, so quite recently (but there are theories that neanderthal had some early forms of agriculture).

Heredity in animals and humans however, is intuitively known since "forever". That mating with healthy individuals is more likely to produce healthy offspring is at the very center of evolution - and knowing about genetic diseases, or at least the concept thereof, immediately follows. A good indicator for this is how much importance pre-modern societies placed on the concept of "blood". Blood was just their way of saying genetics. They knew traits were inherited by the offspring, they just didn't know the mechanics. Also they didn't know exactly which traits were inherited and which not - but then again, neither Mendel did. Farmers and Herders had good eyes for that though.

I'm aware I'm not citing any sources and I'm not saying there aren't, but sometimes it is difficult to say how much people know once, especially in times where the only means of knowledge inheritance was through oral tradition. One might speculate, that in certain areas of botanics they might have even known things we don't know, especially about healing properties of plants and such.

  • I doubt that farmers understood heredity much. Consider the biblical story of Jacob breeding white and black goats to get striped goats. – Michael Sep 9 '14 at 18:08
  • It worked, though. – Oldcat Sep 9 '14 at 18:51
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    @Michael : As I said, they didn't know the specifics, but neither do we fully grasp them. We haven't decoded every genome, we don't know the function of every allele, afaik we don't even know with 100% accuracy which genes will be inherited or which expressed. In any case, just look at the difference between maize and zea. Mesoamerican civilization (meaning Mayas...long before the Europeans came and way before mendel) selectively bred zea to maize and the result (and even the long way to it) is astounding. – Matthaeus Sep 9 '14 at 22:20

Basically people thought that all the traits of your mum and dad would get mixed up in a genetic blender ( to put it simply). Eg, if a black squirrel and a white squirrel had a baby squirrel that baby would be a grey squirrel.

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