Researchers recently learned that Immigration and Customs Enforcement used facial recognition on millions of driver’s license photographs without the license-holders’ knowledge, the latest revelation about governments employing the technology in ways that threaten civil liberties.

But the surveillance potential of facial recognition — its ability to create a “perpetual lineup” — isn’t the only cause for concern. The technological frontiers being explored by questionable researchers and unscrupulous start-ups recall the discredited pseudosciences of physiognomy and phrenology, which purport to use facial structure and head shape to assess character and mental capacity.

Artificial intelligence and modern computing are giving new life and a veneer of objectivity to these debunked theories, which were once used to legitimize slavery and perpetuate Nazi race “science.” Those who wish to spread essentialist theories of racial hierarchy are paying attention. In one blog, for example, a contemporary white nationalist claimed that “physiognomy is real” and “needs to come back as a legitimate field of scientific inquiry.”

More broadly, new applications of facial recognition — not just in academic research, but also in commercial products that try to guess emotions from facial expressions — echo the same biological essentialism behind physiognomy. Apparently, we still haven’t learned that faces do not contain some deeper truth about the people they belong to.