Thursday, March 17, 2016

Fossil dating and context

In this blog post I will be addressing the time period when Ardi lived as well as its habitat. Knowing the age of the fossil is extremely useful in figuring out how Ardi relates to the rest of the hominins and to modern humans. Knowing the environment in which it lived is very important in discovering its locomotion and how it lived in its society.
Most scientists today agree that Ardipithecus ramidus is dated to have lived around 4.4 million years ago, however that was not always the case. Dr. John Kappelman and Dr. John G. Fleagle had an issue with the initial date published, 4.387± 0.031mya. Their argument said that because this date was only taken from stratigraphic markers and was assumed to be the maximum age of the Ardi fossil, there is not enough data to make this assumption. They said that Ardipithecus ramidus should be dated at between 3.89 and 4.39 million years ago. However, further research with argon dating and paleomagnetic data prove that the fossil is dated 4.388±0.053mya, which is very similar to the initial date of 4.387±0.031mya. In my opinion it is better to be challenged and do more research to clarify the date of a fossil than to assume to date based on one piece of evidence (Kappelman).
Past and present.
Ardipithecus's woodland was more like Kenya's Kibwezi Forest (left) than Aramis today (Gibbons).

Ardipithecus ramidus was found in Aramis, Ethiopia, which today is a dry grassland with a few sparse trees. However, the landscape was very different in when Ardi lived there. Research based on fossil bones of other animals found near the Ardipithecus ramidus site showed an abundance of birds as small mammals living around Ardi. The 29 species of birds include parrots and peafowl (Louchart). The presence of peafowl is important because modern peafowl live in open forests and indicates that Ardipithecus ramidus “was close to or in [a] forest, with watercourses” (Pickford). Another study used carbon-isotope techniques of the teeth of five individuals, which showed that “Ar. ramidus ate mostly woodland, rather than grassland, plants” (Gibbons). All of this evidence combines into a picture of Ardi living in a forest instead of a savannah or grassland.

An artist reconstruction of what Ardipithecus ramidus may have looked like in its natural habitat (Matternes).

Before scientists looked at the area around Ardipithecus ramidus and actually studied the fossils, they assumed that bipedalism evolved in a grassland. I think that it was very presumptuous of scientists to think that without any evidence. I am glad that with the discovery of Ardi has come a new, better, understanding of the environment in which humans evolved.


Gibbons A. 2009. Habitat for Humanity. Science [Internet] 326:40. Available from: http://science.sciencemag.org/content/326/5949/40.full

Kappelman J, Fleagle JG. 1995. Age of early hominids. Nature [Internet] 376:558–559. Available from: http://search.proquest.com/docview/204469195?accountid=11667

Louchart A, Wesselman H, Blumenschine RJ, Hlusko LJ, Njau JK, Black MT, Asnake M, White TD. 2009. Taphonomic, Avian, and Small-Vertebrate Indicators of Ardipithecus ramidus Habitat. Science [Internet] 326:66. Available from: http://www.jstor.org/stable/40328574

Matternes J. 2009. Standing Tall. Society for Science & the Public. Available from: https://www.sciencenews.org/article/evolutions-bad-girl

Pickford M, Senut B, Mourer-Chauviré C. 2004. Early Pliocene Tragulidae and peafowls in the Rift Valley, Kenya: evidence for rainforest in East Africa. Comptes Rendus Palevol 3:179–189.




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