I went to the original paper (https://www.frontiersin.org/articles/10.3389/fevo.2021.742639/full https://www.frontiersin.org/articles/10.3389/fevo.2021.74263...

I went to the original paper (https://www.frontiersin.org/articles/10.3389/fevo.2021.742639/full https://www.frontiersin.org/articles/10.3389/fevo.2021.74263...) and this graph of their data: https://www.frontiersin.org/files/Articles/742639/fevo-09-742639-HTML/image_m/fevo-09-742639-g001.jpg https://www.frontiersin.org/files/Articles/742639/fevo-09-74... Long story short I've got some concerns with their analysis. To me it looks like the difference between now and the recent past is mostly just increased variance with a lot more brains on the smaller side. (This is more visible on the graph on the left, where the data points start to fan out as one gets later). 3000 years is also quite recent, and if this is a true effect I'd wonder why it would show up the same way in the Old World, in Australia, and in the New World, each of which were genetically isolated from the others for much longer than that.