The greatest show on Earth

Turning points in human evolution

It’s an ironic commentary on the real condition of our supposedly “advanced” nation that fully 38 percent of Americans are “young-Earth creationists” who, even in the face of today’s overwhelming counter-evidence, believe God created human beings pretty much in their present form at one time within the last 10,000 years. This is according to a 2017 Gallup poll that also found 57% believe humans developed over millions of years from less advanced forms of life, including 38% who believe God guided the process and 19% who believe God had no part in the process.

Some folks like to claim that America is an “exceptional” nation. This turns out to be true when it comes to opinions about biology, but in this case “exceptional” turns out to mean “exceptionally ill-informed.” A poll published in Science magazine on Aug. 11, 2006, found that, when 34 industrialized nations are listed according to their degree of “public acceptance of evolution,” America ranks number 33, just ahead of Turkey.

Creationists are missing out on all the fun. Earth has been alive with the exploits of living creatures for most of the past 4.5 billion years. Richard Dawkins’ wonderful book The Greatest Show on Earth: The Evidence for Evolution relates this saga as seen through the lens of evolutionary biology.

The March 28 issue of Science News, a recommended magazine for science fans, presents three recently discovered examples. The first concerns the evolution of the human foot. We have achieved our evolutionary success partly through our long-distance running ability. For example, the fastest land animal alive, the cheetah, can sprint at 58 mph for several hundred yards. But persistent humans can catch a cheetah by jogging to keep the animal in sight until it becomes an exhausted and relatively easy prey.

This talent comes from the architecture of our foot, especially its longitudinal arch along the inside of the foot and transverse arch across the top of the foot. A recent study suggests the transverse arch evolved more than 3.4 million years ago, and that it provided the rigidity required to walk and run on two feet. Other living primates, such as chimpanzees, have flat, floppy feet that are difficult to walk on because they lack the transverse arch.

The following home experiment can convince your that this transverse arch makes the foot more rigid. Stretch out and hold a wellused dollar bill at both ends, then release one end. The bill just flops downward. Now hold it again in both hands but give it an upward-opening transverse arch by pressing with your thumbs and slightly curling it lengthwise. The bill will stiffen and remain straight when you release one end. It might even cantilever (support) a few coins placed on the released end.

The second example concerns tool-making. At least 15 different human ancestral species populated regions of Africa during the 5 million to 6 million years since humans diverged from chimpanzees and bonobos. It’s been commonly assumed that only the five “Homo” species, namely habilis, erectus, heidelbergensis, neanderthalensis and sapiens, could hand-fashion stone artifacts such as axes and arrowheads, because only the Homo genus had the requisite hand flexibility and strength to make, grip and use such tools. Now there is evidence that Paranthropus boisei, living during 2.3 million to 1.2 million years ago and contemporaneous with Homo erectus, may have had the physical ability to make such tools. The hand bones, along with the strong arms and shoulders of newly discovered fossils suggest that this non-Homo species had at least the physical ability to make and use tools, but whether it actually did make such tools is still an open question.

Third, burying the dead is a behavior previously associated only with Homo sapiens. Now excavations in Iraq’s Shanidar Cave have added to previous evidence suggesting the site contains intentionally buried Neanderthals. Fossils unearthed from the cave, and the surrounding sediment, indicate an individual was placed within a shallow depression that someone had dug. Excavations during the 1950s had already yielded fossils of ten other Neanderthals, including one with pollen from flowers that were apparently scattered around the body in funeral rituals. According to Emma Pomeroy, an archaeologist at the University of Cambridge, “We are pretty convinced that at least some of the Shanidar individuals were intentionally deposited.” Preliminary dating suggests the individuals lived between 70,000 and 60,000 years ago. Another team member comments that “As with all previous claims for Neandertal intentional burials, there are no smoking guns.”

It’s all part of our fascinating evolutionary adventure.