OK, this title is taken directly from the article, but it's wrong. As the paper beneath the headline clearly states, it claims that Khoisan have been the largest effective population through history, a rather different idea. You can be the largest effective population for thousands upon thousands of years of being the smallest population in the conventional sense.
Compare the headline with a nonrandomly-chosen sentence from the paper:
Headline: Khoisan hunter-gatherers have been the largest population throughout most of modern-human demographic history.
Paper: Our hypothesis may [...] suggest that the Khoisan hunter-gatherers and their ancestors have been the largest population in terms of genetic diversity throughout modern-human history. (emphasis added)
Compare the headline with a nonrandomly-chosen sentence from the paper:
Headline: Khoisan hunter-gatherers have been the largest population throughout most of modern-human demographic history.
Paper: Our hypothesis may [...] suggest that the Khoisan hunter-gatherers and their ancestors have been the largest population in terms of genetic diversity throughout modern-human history. (emphasis added)