See https://www.sciencemag.org/news/2021/05/neanderthals-carb-loaded-helping-grow-their-big-brains . The article says in part 'The study is “groundbreaking,” says Harvard University evolutionary biologist Rachel Carmody, who was not part of the research. The work suggests the ancestors of both humans and Neanderthals were cooking lots of starchy foods at least 600,000 years ago. And they had already adapted to eating more starchy plants long before the invention of agriculture 10,000 years ago, she says.'
The article (in the above quote) has an error in suggesting that Neanderthals were not humans. Neanderthals were also humans, though possibly not a subspecies of our species (Homo sapiens) of humans. Neanderthals were in our genus, Homo, and as such they were humans. That is because the word Latin Homo means "Human/Man" and the word Homo as used in taxonomy means "Human/Man". [See https://www.merriam-webster.com/dictionary/homo and https://en.wikipedia.org/wiki/Homo .] There is also genetic evidence that our species (or sub species of Homo sapiens) interbred with the Neanderthals and produced viable offspring - many of us carry some Neanderthal genes.