What did Darwin mean by "genetic connection"?

Submitted by DisgruntledBrDev t3_10ybfaw in askscience

I'm reading "the origin of species", and in ch. 4, under "convergence of character", Darwin, arguing that a same species would be very unlikely to arise from two different lineages, says, and i quote "if this had occurred, we should meet with the same form, independent of genetic connection".

But a quick Google search says that Mendel only published his works on inheritance in 1966, 7 years after Darwin's book was published, and DNA was only discovered in 1869. I find it very unlikely that he'd be able to use the term "genetic" in the same sense as us.

So what the hell did Darwin mean by "genetic connection"?!

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urzu_seven t1_j7yb2oq wrote

The word genetic was coined in the early 1800's (circa 1830) by Scottish philosopher and historian Thomas Carlyle and head that meaning of "pertaining to origins". Darwin used it similarly to refer to biological origins. Although the exact mechanisms and details were not discovered until later, the idea that plants and animals pass on traits has long been known, its what farming and animal husbandry have been based on for millennia. Darwin was simply expanding on that idea to apply to more substantial change over a greater time period. The invention of the word gene and its connection to genetics came later, by almost a century (circa 1910), with the word genetic already having been in use.

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Topazz410 t1_j853ik8 wrote

If I am correct the idea of genes and genetic information being loci on some form of material inherited from parents is credited to Thomas Hunt Morgan.

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NakoL1 t1_j7yd099 wrote

"genetic" here means "ancestry"

Darwin didn't know about genetics in the modern sense or about inheritance (nobody would understand much about that for another 50 years or so; Darwin's own theories on the subject were all over the place, in hindsight) but at that point scientists did know that species were related to one another. Like in the sense that cats and lynxes are related.

so it's in the sense of phylogeny, not reproduction

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_Oman t1_j808r8j wrote

I would say that they didn't understand what the mechanism or exact rules were that influence inheritance, but they certainly understood the basics. There have been texts about parentage and selectively breeding livestock well before Darwin. Darwin helped to put the micro-generation scope in line with the macro-generation scope.

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DisgruntledBrDev OP t1_j811qd9 wrote

A bit later in the same chapter he says "[...] but it serves to aknowledge plainly our ignorance of the cause of each particular variation", and "The evidence that accidental mutilations can be inherited is at present not decisive". Oh, and the first two chapters are dedicated to breeding and human selection, and he legit says "if you went to a breeder and explain our theory about extinct variants being the ancestors of their cattle, they'll laugh at your face".

It seems to me that he understood the basics, but the scientific community was still divided and colecting evidence was quite hard at the time.

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babar90 t1_j8z4q22 wrote

Darwin's book is about inheritance as a broad concept, and the whole point of the book is to refine it a lot and use it to explain the evolution of species.

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PoorlyAttired t1_j7y92ee wrote

That's a great question. Online search says its from the Greek meaning generative and before that, origin.

https://en.m.wikipedia.org/wiki/Genetics#:~:text=11%20External%20links-,Etymology,%CE%B3%CE%AD%CE%BD%CE%B5%CF%83%CE%B9%CF%82%20genesis%20meaning%20%22origin%22.

So probably means the same sort of thing but the later discoveries took that name as well.

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Current-Ad6521 t1_j8ht5c7 wrote

As other commenters mentioned, the word genetic did already exist

This quote essentially uses "genetic connection" in reference to what we now call "blood related"

But the thing that actually is crazy about Darwin in terms of genes is that he discovered natural selection, a phenomenon about genes, without knowing genes existed.

Evolution had be hypothesized / theorized for a long time before Darwin, it dates back to 495–35 BCE. Much of the terms he used in that book are not terms now, but were terms already developed by other evolutionary scientists prior to him using them. "genetic connection" had been used already to mean descended from the same being. The major evolutionist before Darwin was Lamarck, who coined and described many of the terms like that and described them quite accurately. Lamarck knew about inheritance and acquired traits already and did refer to this using terms like genetics, so Darwin did have that information.

Darwin did notice patterns that he assumed must be due to traits the animals must have in order for the patterns to be happening. He usually used the term "undergoing modification". He said many things that were about genes and inheritance without using modern terms before model, he definitely understood and noticed genetic patterns without figuring out what was causing them.

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