Reaching a hundredth birthday is always cause for celebration, but these days there are so many centenarians around that scientists don’t even bother trying to keep track of them all. Indeed, in 2012 the United Nations estimated that there were about 316,600 people over 100 living around the world. By 2050, that number – unbelievably – is expected to rise to over three million.

A much more exclusive club, therefore, are the supercentenarians, or people who live to 110 or older. The Gerontology Research Group, a global team headquartered in Los Angeles, maintains the go-to database for keeping track of the oldest among us. Until this week, there were 53 supercentenarians. Sadly, the death of the oldest, Misao Okawa of Japan, was announced on 1 April. She was 117.

Okawa was born in 1898, and there are now just four living people – three Americans and one Italian, all women – who were born before 1900. That is, they have lived to see three centuries. You might call these four people “tricenta-centenarians*” if giving their group a name (although language experts may have a better suggestion), and what makes them unique is that the world won’t see another set until 2100. This loss will likely happen in less than a decade, as supercentenarians tend to hold their venerated title only fleetingly.

Time’s unrelenting march means there’s a steady turnover of the world’s oldest, causing experts across many fields – biology, history, cultural anthropology – to scramble to learn what they can from these extraordinary people while they are still here. And it’s not only their health secrets that they stand to teach us.