Paleontology. Dental evidence suggests Neandertals matured faster than we do.
Gibbons
Ann
A
D000818:Animals; D003743:Dental Enamel / Q000254:growth & development*; D015186:Hominidae / Q000254:growth & development*; D006801:Humans; D008963:Molar / Q000254:growth & development; D010161:Paleodontology; D014078:Tooth Eruption