08 – Multiple contemporaneous species
3.5 to 3.3 million years ago
Scientists increasingly recognize that multiple hominin species existed at the same time throughout much of human evolution. In fact, the human evolutionary tree grows more bushy with the increasingly complete fossil record.
In 2012, a fossil foot was found in Ethiopia that differed from the contemporaneous fossils known in that region. The foot had long toes and abducted big toe, primitive features that single it out from the australopith species found in the same locality. This taxic diversity in the early hominin fossil record shows that not all ancient hominins developed bipedality, and nonbiped hominin lineages must have persisted for much longer than we previously thought. Such species richness in the fossil record is a far cry from the idea, held for most of the 20th century, that a single hominin species arose and was replaced across evolutionary time.
Image credit: https://monipol.de/photo/hominiden-evolution.html/attachment/naturkundemuseum-berlin-13 (K. platyops); https://www.atlasvirtual.com.br/australopithecusdeyiremeda.htm (A. deyiremeda); ASU Institute of Human Origins (A. afarensis)
Environmental and Climate Changes
Continued aridity, enhanced seasonality—Loss of forests and savanna expansion 4.4 Ma