Lamarck
Do traits gained in life pass to children?
That time, that place
Lamarck had charge of invertebrates at the Paris natural history museum. He coined the word invertebrate, and was among the first to use the term biology.
He set fossils beside living creatures and compared. Again and again he found things that were alike but not the same.
Why this question
So he made a claim that was bold for the time: species are not fixed but change over time.
The question itself was right. The problem was how.
What was found
His answer: organs used heavily develop, organs neglected wither, and the changes so acquired pass to offspring.
A giraffe stretched its neck reaching for high leaves, and the stretched neck passed to its young.
The first half — use strengthens, disuse withers — is called use and disuse; the second half, that such changes are inherited, is the inheritance of acquired characteristics.
It sounded plausible — muscles do grow with use. But changes acquired in a lifetime are not passed on. That is where it failed.
Species were unchanged since creation
The resemblances and mismatches between fossils and living species
In the Soviet Union, Lysenko revived the idea politically, wrecking agriculture and purging the scientists who objected