That was a curious detail in the article. I’m not too sure (for one thing) that the lake is 25 million years old, but regardless, how far down will they be looking? Also, if the intent is to look on the bottom for ancient artifacts washed in when the big glacial dams let go and cubic miles of meltwater tore lose everything in their path and dumped it into the overflowing Baikal, wouldn’t it make more sense to look upstream? ;’)
In the case of North America, between the glacial periods and the periods where the ocean covered much of the land, IMO, most evidence of former inhabitants and their way of life would have been scrubbed from existence.