The Two Million Year Question

Careful studies of 2-million year old human-like fossils just published in the April 12, 2012 issue of Science raise more questions than they answer.

These papers provide highly detailed information about the teeth, rib cage, hands, and feet of this strange relative, known to scientists as Australopithecus sediba.  But we still do not know the answer to the biggest question of all.  How does sediba fit in the human family tree?  Is sediba a direct human ancestor?  If not, why are they so similar to us in some respects?

Photo Credit: The reconstructed skull and mandible of Australopithecus sediba.Reconstruction by Peter Schmid, Photo by Lee R. Berger. Image courtesy of Lee R. Berger and the University of the Witwatersrand.

The teeth are mostly like those of Australopithecus africanus but also quite a bit like the earliest examples of the genus Homo.  That is surprising.  For some experts, it calls into question the standard view that Homo evolved from Australopithecus afarensis, most commonly known as “Lucy.” 

The new analysis suggests an evolutionary pathway from africanus to sediba to Homo.  In that case, Lucy is a relative but not an ancestor.  Sediba is. 

Not so fast, others insist.  The first examples of Homo may go back to 2.3 million years ago, long before sediba appears at just under two million years ago.  Lucy and her afarensis kin lived much earlier, enough to be ancestral to Homo. 

Based on what we know now, the debate will continue because the facts just do not line up neatly or offer a simple story.  "Our study provides further evidence that sediba is indeed a very close relative of early humans, but we can't definitively determine its position relative to africanus,” study co-author Debbie Guatelli-Steinberg said according to a release from Ohio State University.

What these studies do provide is a remarkably complete picture of what early human-like ancestors look like.  They also provide another surprise.  Despite having a foot with a narrow heel, similar to chimpanzees, sediba definitely walked upright, maybe even using a somewhat awkward never known before to scientists.  They were clearly not knuckle-walkers, like the apes, but they were not nearly as graceful as the humans who followed.  It seems they walked upright differently.  

For now, what all this suggests is that the story of our deep ancestry is more complex than we usually imagine.  Straight ancestral lines are hard to draw.  More finds may help sort things out.  But they may also add new complexity.  The way it looks, multiple forms of early human life may have existed at once.  They differed slightly from each other and also in the degree to which they resemble us.  That makes it very hard to sort out the lineages.  

Is sediba a direct human ancestors?  Yes, at least according Lee Berger, who discovered sediba in a pit in northern South Africa in 2008.  Most experts, however, argue no, mainly the dates are out of line.  What difference does it make?  Perhaps the biggest significance of this debate is to show us that the more we know, the more we see a complex picture of multiple species and perhaps interweaving lineages, making it all the more remarkable that we are here at all. 

This research is published as a set of six research reports in the April 12, 2012 issue of the journal Science, a publication of the American Association for the Advancement of Science. 

Brain Stimulation and Human Cognitive Enhancement

Who wouldn't want to be smarter? And what parents don’t want academic success for their children?

Now it appears that simple electrical devices that stimulate the brain are able to enhance human cognitive performance.

An Essay in a recent issue of Current Biology describes recent advances in “non-invasive brain stimulation” (NIBS). One approach in particular—“transcranial direct current stimulation” or TDCS—is described in detail. According to the essay, TDCS is a simple tool that is “portable, painless, inexpensive, apparently safe, and with potential longterm efficacy.” It may be used to help those suffering from impaired cognitive abilities.

More to our point, however, is that TDCS shows remarkable potential for human enhancement. Simply put, this device seems to have the power to make normal children and adults smarter than they would normally be. To quote the essay, TDCS has the potential “to enhance fundamental human capacities, such as motor and sensorimotor skills, vision, decision making and problem solving, mathematical cognition, language, memory, and attention—improvements that seem to persist without apparent cognitive side effects.”

The main point of the essay is to invite broad discussion about the neuroethics of cognitive enhancement. A good deal of attention is focused on whether TDCS or similar techniques should be used on children. The authors argue that having smarter children will benefit everyone. Their conclusion: “If it is handled judiciously, TDCS could prove to be an inexpensive and widely-deployed technology with substantial benefits to individuals and society.”

Anyone following the debate about human enhancement will see this as further evidence that in terms of the technology, “the future is here.”

Sure, there’s a lot to think about here before we rush out and strap TDCS devices on our heads. Anyone worried that mobile phones pose a health risk will probably not think this is such a good idea.

But many of us human beings value our cognitive abilities above everything else. If TDCS is a safe way to become smarter, then why not?

According to the Christian tradition, human beings are created in the image of God. One way we resemble God is through the power of intellect, which we share with the animals but which we alone exhibit to such a lofty degree that we can be compared to God. According to Gregory of Nyssa, one of the great theologians of the fourth century, “The Deity beholds and hears all things, and searches all things out." No surprise there. But then Gregory adds: "You too have the power of apprehension of things by means of sight and hearing, and the understanding that inquires into things and searches them out.”

How expected that by inquiring into all things and searching them out, we now seem to be learning how to enhance the very power of thought and discovery.

If we enhance our intelligence will we become more like God? Not quite. Intelligence may be one way we can and should resemble God, but it's not the only way. In fact, intelligence by itself can be worrisome.

Much to his credit, Julian Savulescu (a co-author in the TDCS essay) is one of very few who has urged us to pay attention to the question of “moral enhancement.” Quite simply, smarter people who are not also morally better people may turn out to be very dangerous people. So after reading the essay on how to enhance cognition, let me suggest you look at a 2008 paper by Ingmar Persson and Julian Savulescu, entitled "THE PERILS OF COGNITIVE ENHANCEMENT AND THE URGENT IMPERATIVE TO ENHANCE THE MORAL CHARACTER OF HUMANITY."

Evolutionary Fast-Track for Human Brains

More than 35 years ago, Allan Wilson and Mary-Claire King made an astonishing proposal. Maybe what separates humans and chimps is not just our genes. Maybe it’s also how our genes are expressed or regulated.

Research published in today’s issue of PLoS Biology builds on decades of intervening advances in evolution and genetics and take the question much further. The difference between humans and nonhuman primates in cognitive ability is explained in large part by differences in gene expression, especially during the critical periods when young brains are being formed.

Humans share many of their genes with other species, especially chimps. In fact, we share so many genes that it is hard to explain how we can be so different in terms of cognitive ability. If genes make all the difference, how can they explain the differences between chimp and human brains? And how can a mere six million years of human-chimp divergence give us enough time to accumulate enough genetic change?

The answer seems to lie in the relatively rapid evolution of differences in gene expression. In other words, while the genes themselves evolved slowly, the regulation of their expression evolved more rapidly. It’s not just the genes but their expression that’s important. It’s not just the evolution of genes but the evolution of gene expression that drives the rapid divergence between human and chimp brains.

This is especially true in the genes that control the development of the prefrontal cortex of the brain. In other words, there has been relatively rapid evolution in the genetic mechanisms that regulate genes directly responsible for the early-childhood neural development of the critically-important prefrontal cortex, which is involved in abstract thinking, planning, social intelligence, and working memory.

According to the article, “humans display a 3-5 times faster evolutionary rate in divergence in developmental patterns, compared to chimpanzees.” Most important, however, is the way this research identifies specific regulators that have evolved rapidly since human-chimp divergence. These regulators are “micro-RNAs,” some of which are specifically identified in the article, with the claim that “changes in the expression of a few key regulators may have been a major driving force behind rapid evolution of the human brain.”

According to the study’s senior author, Philipp Khaitovich, this finding suggests that "identifying the exact genetic changes that made us think and act like humans might be easier than we previously imagined." Kkaitovich was quoted in a press release issued by the journal, PLoS Biology.

The article is entitled "Micro-RNA-Driven Developmental Remodeling in the Brain Distinguishes Humans from Other Primates" and appears in the December 6 issue of PLoS Biology, where it is freely available to the public.

Science and Human Mystery

I have been reading Bernard McGinn, a foremost expert on the history of Christian spirituality and mystical theology. In a recent essay, he comments on “the importance of recognizing the mystery of human existence.”

In Christian theology, the mystery of the human is grounded in the mystery of God. In the fourth century, St. Gregory of Nyssa observed that human beings are in the image of God. Our nature mirrors God’s nature. If God is inexhaustible mystery, then what we are must always remain a mystery to ourselves. Otherwise, our knowledge of ourselves would serve as something of a key for us to figure God out, a kind of theological Rosetta stone.

What does this have to do with recent science? Some think that science finds facts and dissolves mysteries. McGinn suggests as much. He thinks that theology’s insistence on human mystery serves as a useful check on the de-mystifying pretensions of science.

I agree with McGinn about the theology of essential human mystery. But I disagree that science has a tendency to erase mystery. Sure, many people see science that way. But look again. The more we learn about human origins, the more we find that any clear notion of a distinct human species seems to unravel. The more scientists merge human and nonhuman organisms or blur the distinction between human and machine, the more we make ourselves mysterious.

If I am right, science increases mystery. At least that’s what I tried to suggest in the brief article I contributed to Science last February. For more, see my post for October 12, below.

That’s why I think McGinn is not quite right when he say this:

“If God is the ultimate mystery, man’s image-nature implies an essentially negative horizon, or limit, to all that can be scientifically discovered about humanity, however original, illuminating, and productive these findings may be. From this viewpoint, growing scientific information (i.e. more and more facts) about human nature (biological, psychological, and sociological) will always be limited by the realization that the true meaning of human existence rests in its status as an inexhaustible mystery. Scientific contributions to the deeper understanding of human nature are welcome and often useful in the task of human self-realization, but they take on a different color when viewed from the sapiential perspective of the “learned ignorance” (docta ignorantia) that recognizes the limits of what can be known and quantified about humanity. This recognition of the limits of science may not be an easy message for contemporaries to appreciate, enamored as we are by the amazing discoveries about homo sapiens made during the past century; but it is one of the most significant challenges that image dei anthropology offers to the present.”

McGinn’s essay is entitled “Humans as Imago Dei: Mystical Anthropology Then and Now.” It appears in Sources of Transformation: Revitalising Christian Spirituality, 2010.