Last names are handy for more than constructing family
trees—they can also trace population connections and movements
across and between countries. Researchers in China recently
mapped the country's so-called isonymy structure, which shows
how likely people are to share their last name with those around
them. The resulting patchwork matches patterns of ethnic
distribution and tracks some of China's historic migrations,
such as the diversity of people who settled in the Yangtze River
basin over many centuries. Such basic surname calculations, the
authors say, can offer quick insight into cultural dispersal in
the world's most populous country. Surnames can act as stand-ins
for genetic markers that fathers pass to their children. Like
genes, family names are subject to random drift: Over time,
certain names become more prevalent than others purely by
chance. A region with high surname similarity indicates that a
stable population has inhabited the area long enough for drift
to take place. A region of low surnam