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GUEST:
Dr. Donald Johanson
Director, Institute of Human Origins
Arizona State University
HOST:
America Online
DATE:
May 8, 2002
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HOST: Good evening, and welcome to this evening's special chat. With us this evening is Dr. Donald Johanson, the anthropologist who discovered "Lucy", a 3 million year old link to our past. It was in the Afar region of Ethiopia that Dr. Johanson made the discovery that changed our understanding of human origins forever. There, in 1974, he found the fossilized remains of a female hominid the world came to know as Lucy. Until then, paleoanthropologists had had to content themselves with the most fragmentary remnants of our pre-human ancestors. Over 40 percent of the Lucy skeleton had been preserved, enough to provide the anthropological world with some startling insights. Today, Donald Johanson is Director of the Institute of Human Origins at Arizona State University in Tempe, Arizona. Now, a new find, named "Orrorin", may allow scientists to trace human evolution more than twice as far back as Lucy. In December 2000, Martin Pickford and Brigitte Senut of the prestigious College de France announced their discovery of 13 hominid bones, found within a volcanic layer that had been previously -- and reliably -- dated at six million years old. With us now to discuss these various finds and answer your questions, Dr. Johanson. Good evening doctor!
gevans18: What led you to believe that Lucy was a direct link to homo sapiens and not a completely different species?
Dr. Johanson: We never really stated that Lucy was a direct link to homo sapiens because the human family tree has many different branches. So, we can't be certain, that she herself was actually on the direct line. We are certain that her bones are so different from other early humans, or human ancestors that she was a distinctive and different species.
Gronti2: Who's the better biped? Lucy or Orrorin? ;)
Dr. Johanson: We don't know enough about Orrorin to be able to characterize its abilities for bipedalism. Since, Lucy is so much more complete we can say that she was a pretty efficient biped.
Browserbo: Dr, what do you say to the people that argue you found an ape that didn't even necessarily walk upright?
Dr. Johanson: The difference between an apes's skeleton, a creature that walks on all fours, and a human ancestor that walked on only two legs is very obvious in the anatomy of the knee and the hip. Lucy's hip, or pelvis, was wide and short from top to bottom. Resembling a modern human pelvis, very different from the pelvis of a four-legged animal like an ape that is very narrow and high from top to bottom.
PorchTwo: Have any DNA tests been possible with Lucy (teeth or anything)?
Dr. Johanson: The oldest DNA we have from a human ancestor is from a Neanderthal that takes us back to about 100,000 years. Unfortunately, the process of fossilization destroys all of the DNA evidence. So, we do not have any DNA from early human ancestors like Lucy.
McYeck: What are your current projects or interests?
Dr. Johanson: Our current research projects at the institute continue to focus on the period of time when Lucy lived and recently in Ethiopia, we found another skull of her species. The other area of interest, is in the emergence of modern humans. One of my colleagues, Professor Marean, recently announced the discovery in South Africa of 70,000 year old bone tools meaning that they are twice as old as those found in Europe.
Muskox93: Could some of the differences in the various sub-species be accounted for by mere sexual dimorphism?
Dr. Johanson: Normally, we do not recognize sub-species in the fossil record. However, it is clear that differences in size, for example at the Lucy site, represent fossils of males and females. Therefore suggesting that sexual dimorphism was present in Lucy's species.
Browserbo: Would you compare Lucy's link to modern man to be similar to that of the Neanderthal? A closed link?
Dr. Johanson: We can always say that any fossil we find had ancestors, but it is very difficult to tell if they left descendants. However, we have hypothesized that Lucy's species did give rise to later species. Whether those species in turn gave rise to modern humans, is still for many people an open question.
DelCyclist: Would genetic drift between apes and humans indicate when the split occurred as it has in determining "Eve"?
Dr. Johanson: The genetic similarities and differences, between modern humans and modern chimps suggests a relatively recent common ancestor by using the amount of difference in DNA. ... Geneticists have suggested that we shared a common ancestor seven to ten millions of years ago. This is interesting, because when I was an undergraduate student, scientists wanted the split to be 15-20 million years ago. We now know using genetics that the split was much more recent.
DarkSydOTheMoon: What is current geopolitical situation in Ethiopia/East Africa in the context of allowing more digs in far and adjacent regions?
Dr. Johanson: The Ethiopian government particularly the minister of culture actively encourages research groups to conduct field work. There are several expeditions active in Ethiopia at the moment and including some expeditions for the very first time under the leadership of Ethiopian scholars. So, in short ... the situation is very favorable.
McYeck: How do your modern human findings fit with Bryan Sykes' research -- SEVEN DAUGHTERS OF EVE?
Dr. Johanson: Bryan Sykes' work deals more with contemporary humans, while as my research deals with very ancient humans. But the emphasis of his work does find support, in fossil finds of early modern humans.
Mean Ol Engineer: What was it like once you knew what you found?
Dr. Johanson: Thinking back to November 1974, I still feel the sense of tremendous excitement realizing that I had found parts of a skeleton dating to more than 3 million years. I think that moment of excitement for me may never be repeated in my life. But the real reward of finding Lucy was when I realized she was a new species of human ancestor that allowed us to better understand the human family tree.
Gronti2: Is there a standard amount of fossil material you need to make an assumption about a creature's walking stance? What part of the body is the best indicator?
Dr. Johanson: The best indicators of locomotion in these early hominids is located in the knee and in the pelvis. The preservation of Lucy's pelvis is an oddity for us because the pelvis is made of such fragile, thin, bone. It is more common to find parts of a knee especially the bottom end of the thigh bone. This is a dead give away to tell us if that creature walked on two legs or four legs.
Muskox93: What do you believe accounted for the hominid radiation of the past 5 million years?
Dr. Johanson: I think that hominids were isolated over the African Continent in distinct ecological settings, and through the process of evolutionary change they developed into different and distinct species.
PorchTwo: I have had the great pleasure of reading [your books] BLUEPRINTS: SOLVING THE MYSTERY OF EVOLUTION and LUCY: THE BEGINNINGS OF HUMANKIND. Anything else in prospect?
Dr. Johanson: For more information on human evolution consult The Institute of Human Origin's Web site at www.becominghuman.org. The last book I did, which is one of my favorites, was entitled FROM LUCY TO LANGUAGE. This was published in 1996 and contains for the very first time stunning photographs, life size, of all the major important fossil hominid discoveries.
PorchTwo: Thank you
McYeck: Would you describe the climate of Lucy's environment?
Dr. Johanson: We have some idea of the world in which Lucy lived, from the fossilized remains of the contemporary animals. ... the animals that lived with Lucy. And also from aspects of geology and even fossilized pollen-grains. What is most interesting is that the fossil animals and geology as well as pollen, suggests that Lucy lived in a more forested environment than we had previously believed. The general view was that these early ancestors lived in open savannah. But we are now documenting that the earliest ancestors,including Lucy, lived in more forested environments.
Mags1745: Does the Ramipithicus theory still stand about being the missing link?
Dr. Johanson: Ramipithicus is now considered to be an ancestor to modern orangutans, the early suggestion in the 1960s that Ramipithicus was a link between apes and humans was based on an erroneous reconstruction of the upper jaw. Now that more complete specimens have been found in Pakistan, it is clear from the shape of the face, especially that it represents an ancient ancestor to modern orangutans.
ausdia5: Hi. I used to take anthropology course years ago -- forgive me for being rustic -- can you refresh me about the Java man?
Dr. Johanson: Well ... I'll have to talk to Starbucks. ... Just joking! Java man is now known as Homo Erectus, it was found initially in the late 1800s by a Dutchman. What is most interesting about Java man today, is first of all, it has been dated to well over a million years. Suggesting that our ancestors left Africa, much earlier than previously thought and secondly, some fossils of this species have been found in relatively recent sediments. ... Perhaps only 30,000 years ago. Suggesting that Java man was a separate independent line in the far East that did not evolve into modern humans.
ausdia5: Interesting. Thanks for the input!
DelCyclist: The human knee is so poorly adapted to high impact bipedalism that one would think that in 6 million or even 3 million years we would have evolved something better. Your thoughts?
Dr. Johanson: One has to remember that our ancestors did not run or jog on concrete or asphalt pavements. This is one of the reasons why I caution my friends who are joggers, to not spend too much time running on such hard surfaces. It is damaging to the knee and I suspect that not only did our ancestors not run on hard pavements ... but that most of the time was spent in a more leisurely walking mode of locomotion. Yes, cycling is certainly better on the knee.
DelCyclist: Thank you. I can now tell runners we were not evolved for running on pavement -- get a bike!
EastCoastKid17VA: How can there be a different number of chromosomes in the species that are our ancestors? Mutation?
Dr. Johanson: There is not a different number of chromosomes in our ancestors, as far as we know ... there is a different number of chromosomes in modern humans and modern chimps. This is due to reorganization, or an attachment of two different chromosomes in chimpanzees ... but the same genetic information is contained in that fewer number of chromosomes.
Mags1745: Are there indications that our blood "types" have changed over the years?
Dr. Johanson: The only indication that our blood types have changed over the years is the diversity of blood types within human populations. So, I suspect that there has been a change over time.
Muskox93: Is there any evidence that Lucy and/or her contemporaries used tools of any kind?
Dr. Johanson: Very, very good question! In all of the research and excavation that we have conducted in Ethiopia.. we have found the evidence of stone tools ... in the geological deposits that have yielded Lucy and other members of her species. However, when we look at modern chimps, we see that they sometimes used perishable objects like wood, or blades of grass to extract termites from termite mounds. I believe Lucy and her species would have used rudimentary tools such as these. The earliest evidence for our ancestors making and using stone tools ... is about two and a half million years ago. This appears to be associated with the earliest evidence for our own genus ... "Homo".
Mean Ol Engineer: What do you think the near future holds for early humanoid discovery?
Dr. Johanson: I think that we will continue to be surprised by an increasing number of different species of early human ancestors. I also would say that when I am asked,"What do we expect to find?"I always reply, "The unexpected."
HOST: This concludes tonight's special chat with Dr. Johanson! Thank you everyone for coming!! Thank you so much Doctor for sharing your time with us all.
Dr. Johanson: I appreciate this opportunity to chat with all of you ... and I am thrilled to know that there are so many people interested in this wonderful puzzle of how we became human. Goodnight folks! Good night everyone!
HOST: Be sure to visit www.becominghuman.org for more information. Good night all!
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