The third part of the exhibit, “Finding Your Human Ancestry,” goes more deeply into the details of those past 7 million years of human evolution. On hand are fossil casts of famous African, Asian, and European hominids made by the museum’s casting program. Over 200 of these durable epoxy casts are in the Surviving exhibit, and many of the displays can be touched, allowing visitors to not only see the evidence but to feel it. (In all, Monge and her colleague in the casting program, museum volunteer Lisa Gemmill, have created some 3,000 molds and casts covering the stretch of human evolution, many of which are loaned to institutions worldwide for their own exhibits.)
Included in Surviving are casts of the remarkable footprints preserved in volcanic ash made by three bipedal hominids with feet like ours who sauntered through a part of Tanzania, East Africa, around 3.7 million years ago; a skull cast of Sahelanthropus tchadensis, unearthed in Chad, and a cast of the femur of Orrorin tugenensis, from Kenya, both casts representing our oldest known hominid ancestors going back 6 to 7 million years; the diverse australopithecines (including Lucy, from Hadar, Ethiopia, dating from about 3 million years ago); Homo habilis and Homo erectus, both dating to around 2 to 1.5 million years ago; and on to early modern humans and Neanderthals, as well as modern humans.
Having all these family members in one space helps the visitor fully grasp the longterm trends of human evolution: an enlarging brain size and cranium in conjunction with a jutting larger face that starts to get smaller to fit under the brain; a mouth that likewise goes from big (when jutting out from the face) to small in order to fit in the new alignment under the larger cranium; a clearly upright mode of walking with forward-facing toes and a less flexible big toe than other apes; and a pelvis that is wider (to be able to support upright walking) but not so wide as to lose the efficient angle between the knee and hip joint that allows efficient bipedal movement. Less tangible but simultaneous trends include development of language and complex thought, physically evident in the form of early tools and works of art such as the Venus of Willendorf figurine, as well as certain expanded areas of the brain.
“Witnessing Evolution,” the fourth section, offers the actual wordsin dramatically performed audio displaysof famous scientists who have contributed to our knowledge of life on earth. These luminaries include Carolus Linnaeus, Charles Darwin, Thomas Henry Huxley, Joseph Leidy M1844 (professor of anatomy and founder of Penn’s department of biology), Jesuit priest and scientist Pierre Teilhard de Chardin (who said, “Christ is realized in Evolution”), Rosalind Franklin, and Mary Leakey.
By the fifth section, “We Are Not Perfect But We Are OK,” things start getting personal. Though we are successful creatures because we are still here and still evolving, our bodies have some limitations shared by people all over the worldand some of these imperfections are also evidence of the path our evolution has taken.
This part of the exhibit features “Ms. Big,” as Mann and Monge call hera high-tech mechanical model of a modern human female measuring 16-feet from head to toe. One side of Ms. Big’s body is on rails; you can move her limbs to see how arms, joints, hips, knees, and legs work. On the other side are x-ray-like interactive displays that allow a deeper inquiry into our evolutionary anatomy. How our bodies workboth the grace and the imperfectionscan be explored via the multidimensional giant or thematic sections set up on the edges of the giant’s space.
That nagging lower back pain, for instance, is the consequence of our s-curve, required to position our spine upright over our pelvis. Also, while many of us still inherit the set of 32 teeth our earliest ancestors had, albeit on a smaller scale, these teeth must fit within our smaller faces and mouths. The resulting tight fit often leads to removal of our wisdom teeth (one way human culture intervenes with its biology). And there are more imperfections, from the development of osteoporosis as we age, to the risk of stroke from our large brains that require a reliable supply of a lot of blood to keep functioning, to that troublesome runner’s knee or tennis elbow.
Perhaps the most fascinating evolutionary complex and imperfection concerns our big brains, pelvises, and giving birth. First, as we evolved to be two-legged walkers, our hips could only get so wide before compromising the angle between the hip and the knee that makes walking on two legs possible. Next, our brains also evolved into a bigger size than those of our ancestors of a few million years ago.
Two “solutions” to the big-brain-small-birth-canal dilemma evolved: the skull bones in human infants don’t suture until after birth, allowing the edges of each plate to overlap as the head passes through the birth canal; and the human baby is born more helpless than most animals’ young because its brain doesn’t grow to its full capacity until after birth: in the first year of life, a newborn’s brain doubles in size.
This, says Monge, is a “great example of selection for increases in brain size eventually both producing and solving the ‘obstetrical dilemma.’ [Here is] a species that, without modern medical intervention practices, has negative maternal/infant birth outcomes 20 percent of the time. One solution [is] the production of immature offspring that are so underdeveloped that they are best described as extra-uteral fetuses! The biological and social implications of this affect us to the very core of our humanness.”
Our development of culture can intervene in solving problems that arise in the environment and with our bodies. Caesarean sections, artificial joints, jogging, diet programs, and antibiotics are all examples of how we interact with our biology culturally. Though they are having an effect on our evolution, we can hardly begin to predict how.
In the sixth and final section of Surviving, “We Keep Evolving,” both visitors and experts are invited to contemplate what our evolution might look like in the future. What might be the effect of population growth? Genetic manipulation? Natural disasters? The outbreak of a globally spreading disease? Large-scale war? Human-induced environmental alterations?
Which brings up another reason for the urgency of understanding our place in the web of life. “There are deep implications for being aware that we evolved a certain way,” emphasizes Mann. “Our future depends on our ability to recognize our place in nature. If we don’t successfully get at that, we will have the future of another species and become extinct.”
Beebe Bahrami Gr’95 (www.beebesfeast.com) is a frequent contributor to the Gazette. Her book, The Spiritual Traveler SpainThe Guide to Sacred Sites and Pilgrim Routes, will be out in the spring of 2009 from HiddenSpring Books/Paulist Press.
On Surviving and on evolution: www.Surviving-PennEvolutionExhibit.org. This site is also going to be an extensive resource for teaching evolution.
On The Year of Evolution: www.yearofevolution.org.
On the Penn Museum’s casting program: www.PennFossilCasting.com.
FEATURE: Fit Enough, by Beebe Bahrami
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©2008 The Pennsylvania Gazette
Last modified 04/28/08