Today there is only 12 flightless bird families on earth. Nearly30 families have some flightless species that have gone extinct in the last few thousand years, almost all due to human impact.
These are numbers revealed in study from the University of Gothenburgthat is published in Science Advances. Extinct flightless birds makes it hard for scientists to understand the evolution of species diversity, something the first author of the study, Ferran Sayol, hope this study will change.