[1] Univ Kent, Sch Biosci, Canterbury CT2 7NJ, Kent, England
[2] Aspinall Fdn, Port Lympne Reserve CT21 4PD, Kent, England
[3] Natl Museums Scotland, Dept Nat Sci, Chambers St, Edinburgh EH1 1JF, Midlothian, Scotland
[4] Univ Edinburgh, Sch Geosci, Drummond St, Edinburgh EH8 9XP, Midlothian, Scotland
[5] Leibniz Inst Primate Res, German Primate Ctr, D-37077 Gottingen, Germany
[6] Univ Kent, Durrell Inst Conservat & Ecol, Sch Anthropol & Conservat, Canterbury CT2 7NR, Kent, England