New Harvard study
This may come as a set back to scientists who have cited primate studies as a basis for understanding tooth development, age, etc. in pre-historic human remains.
Professor Tanya Smith, together with Professor Richard Wrangham, and Postdoctoral Fellow Zarin Machanda, all from the Department of Human Evolutionary Biology at Harvard, used exciting and brand new methodology for their study published in the Proceedings of the National Academy of Sciences: the primates were photographed (using digital high resolution cameras) in their natural habitat at differing stages of their development.
It was discovered that many young chimps kept on nursing just as much, if not sometimes more, after their first molar tooth had erupted. This certainly upsets findings from any previous studies.
Previous research inaccurate?
Professor Tanya Smith said that when research had previously been released, already about twenty years back, a very definite correlation had been shown between the arrival of the very first molar and weaning.
This information in turn had been reflected by scientists onto records of human fossils, in an attempt to determine the age, size and development of teeth in early humans. Because of the latest research, however, it now seems that chimpanzee tooth development and weaning is not at all an accurate way to estimate what early human children were like.
One of the factors that could explain the difference in the earlier and newest study results is that previously it was only possible to observe chimpanzees in captivity, or to study captive primates’ skeletons. There is evidence to suggest, however, that chimpanzees in captivity grow much quicker compared with wild chimps.
Therefore in the case of comparing data from captive primates and early humans, it seems that the captive chimpanzee’s early development would be quite misleading when placed in the context of pre-historic humans. Chimpanzee skeletons offer no further improvement, because this meant that primate remains needed to be carefully identified, catalogued and an exact age should be assigned to them. This is of course highly difficult, if not impossible, to achieve in their natural habitats.
A unique new technique
A singular technique was therefore devised by the Harvard team: Tanya Smith, Richard Wrangham, and Zarin Machanda worked together with wildlife photographers in the Kanyawara chimpanzee community in Kibale National Park in Uganda, where the photographers were stationed and ready at all times, during months and months of research, taking photographs of the young chimpanzees mouths whenever they were opened – no mean feat! But because the same chimpanzees were photographed successfully over a long period of time, the researchers were able to see exactly when the chimps developed their first molars and then compare the photographs with data.
This latter was information gathered by the researcher on the chimps’ behaviour, including eating habits and weaning. The team of researchers say that they were rather surprised at the results.
The chimpanzee youths were observed moving onto solid foods as their molars developed, beginning to eat the same foods as the adult chimps did, but as suggested by previous studies, this did not necessarily bring on weaning. On the contrary, Tanya Smith confirms that most of the chimpanzees continued to suckle, many in fact increasing their suckling.
Food for thought
This new information, Zarin Machanda thinks, will probably be something that researchers will want to look at in future studies. Machanda continued to say that their next project, which they are already working on is concentrated on observing and recording chimpanzee growth and size at different ages, as well as looking into the reasons why young chimpanzees continue to suckle, despite having the teeth to chew and digest solid foods like adult primates do. There is clearly something that the chimpanzees try to gain by regularly suckling, she said.
Machanda found it particularly fascinating that baby chimpanzees could sometimes be seen behaving rather like two year old human children would: when chimpanzee mothers sometimes refused to let them suckle, the junior primates would throw tantrums.
At times, the mothers would actually cover their breasts with their hands, refusing to allow their offspring to feed and this in particular could provoke displays of anger by the babies. Tanya Smith concluded that not enough studies have been made into infant chimpanzees’ development into adults, in terms of feeding.
She thinks that future research should look at different aspects, such as what foods young chimps choose and how long they suckle, and how long it takes them to eat solids. This, she reckons, will show more conclusive results as to teeth development and weaning than previous studies ever could.
One thing for certain that can be learned here: the use of chimpanzee tooth development as a proxy for pre-historic human studies now needs to be re-evaluated. Hopefully new studies that will spring out of interest in the Harvard research team’s results, will continue to shed light on this fascinating subject.
Johanna Bergstrom is a blogger and content writer who enjoys sharing her ideas on beauty, health and communication techniques with her readers. Currently she is associated with AceDentalResource where people can get high quality dental veneers for those perfect shiny teeth.