This week’s pho­to essay looks at the the­o­ry of evo­lu­tion using the Maropeng exhi­bi­tion as a back­drop. Charles Dar­win (18091882) is world-renowned for his the­o­ry of evo­lu­tion. In his book The Ori­gin of Species by Means of Nat­ur­al Selec­tion, Dar­win argued the case for nat­ur­al selec­tion – that over time crea­tures which are able to adapt bio­log­i­cal­ly to changes in their envi­ron­ments (in oth­er words, evolve) sur­vive, while those that don’t adapt become extinct.

It’s only in the past 50 years or so that the the­o­ry of evo­lu­tion has received wide-scale accep­tance. Anatom­i­cal indi­ca­tions which sup­port the con­cept of evo­lu­tion can be seen in hominid fos­sils from the Sterk­fontein Caves and oth­er sites in the Cra­dle of Humankind.

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The hominid fam­i­ly tree has a large num­ber of branch­es. Although researchers agree on the gen­er­al trends of hominid evo­lu­tion, the rel­a­tive scarci­ty and frag­men­tary nature of fos­sils and time gaps in the fos­sil record leave room for debate.

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The devel­op­ment of the brain enabled hominids to make and use tools and fire, com­mu­ni­cate using lan­guage, devel­op cul­ture and soci­ety, adapt to new envi­ron­ments and, final­ly, to become self-aware and creative.

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In the 19th cen­tu­ry, zool­o­gists began to the­o­rise about the evo­lu­tion of humans from ape-like ances­tors. This pic­ture shows an exam­ple of the evo­lu­tion of the genus known as Homo, in which we as Homo sapi­ens belong. There have been many species in the human fam­i­ly tree belong­ing to the genus Homo in the past 2.3-million years or so.

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Mod­ern humans are grouped togeth­er with all ear­li­er species of the zoo­log­i­cal fam­i­ly Hominidae as hominids. We are the most recent branch of a fam­i­ly tree that over mil­lions of years has includ­ed dozens of hominid species. But we – Homo sapi­ens – are the only hominids still liv­ing today. We have been around for only about 200,000 years. Our fam­i­ly tree is rel­a­tive­ly young. Hominids appeared only about 7-mil­lion years ago. By com­par­i­son, the last dinosaurs died out 65-mil­lion years ago. The Earth was formed about 4.6-billion years ago and the uni­verse was born about 14-bil­lion years ago.

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The genus Homo includes not only Homo sapi­ens, but also many ear­li­er species of Homo that are now extinct, includ­ing Homo habilis, Homo ergaster (in Africa), Homo erec­tus (in Europe and Asia), Homo ante­ces­sor, Homo hei­del­ber­gen­sis and Homo nean­derthalen­sis (in Europe).

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