  In many developed countries, human life expectancy has doubled over the last
180 years from ~40 to ~80 years. Underlying this great advance is a change in
how we age, yet our understanding of this change remains limited. Here we
present a unique database rich with possibilities to study the human ageing
process: the AgeGuess.org database on people's perceived and chronological
ages. Perceived age (i.e. how old one looks to others) correlates with
biological age, a measure of a person's health condition in comparison to the
average of same-aged peers. Determining biological age usually involves
elaborate molecular and cellular biomarkers. Using instead perceived age as a
biomarker of biological age enables us to collect large amounts of data on
biological age through a citizen science project, where people upload pictures
of themselves and guess the ages of other people at http://www.ageguess.org. It
furthermore allows to collect data retrospectively, because people can upload
photographs of themselves when they were younger or of their parents and
grandparents. We can thus study the temporal variation in the gap between
perceived age and chronological age to address questions such as whether we now
age slower or delay ageing until older ages. The here presented perceived age
data span birth cohorts from the years 1877 to 2014. Since 2012 the database
has grown to now contain around 200,000 perceived age guesses. More than 4000
citizen scientists from over 120 countries of origin have uploaded ~5000 facial
photographs. We detail how the data are collected, where the data can be
downloaded free of charge, and the contained variables. Beyond ageing research,
the data present a wealth of possibilities to study how humans guess ages and
to use this knowledge for instance in advancing and testing emerging
applications of artificial intelligence and deep learning algorithms.
