On the Origin of Our Species: Understanding the Newest Discoveries
New specimen discovered in Morocco raises questions about our evolutionary development.
Before You Read
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Our understanding of human origins has changed quite dramatically in just a few short weeks. First, there was the finding (described in these two BioLogos posts) that fossils of the petite-brained Homo naledi were only about 300,000 years old, much younger than scientists had predicted. At that point, the earliest unambiguously identified fossils of our species were 195,000 years old. This past week that changed dramatically—by over 100,000 years. What characteristics did our species exhibit when it was much, much newer? The answer is interesting indeed.
315,000 year-old fossils of individuals who looked much like us have been identified in Morocco. The lead investigator, Jean-Jacques Hublin of the Max Planck Institute, describes these individuals as possessing “a face you could cross in the street today.” But the investigators go on to show that even though their face was much like ours, they were significantly different as well. Their brain case was elongated, not globular like ours, and their brow ridges were thicker (see the Figure above from Stringer and Galway-Witham, 2017). These individuals, in the words of Hublin et al. (2017), had “a mosaic of features.” On the one hand their facial, mandibular and dental morphology were aligned with anatomically modern humans, but their neurocranial and endocranial morphology were considerably more primitive. In other words, their faces looked like modern humans, but the rest of their heads didn’t. It seems likely then that evolution of the face preceded the changes in the brain case. Mosaicism (old and new features together) was a defining feature of Homo naledi as well. Investigators have been taken by surprise. They expected a gradual set of changes with most aspects of the morphology becoming increasingly modern in a continuum. Instead they see mosaicism—the body seems to changing in highly discrete “packages,” leaving other parts largely unchanged.
Remarkably, mosaicism appears to have characterized Neanderthal evolution as well. In 2014, some of the DNA from a set of 430,000 year old hominin fossils from a cave in Spain was successfully sequenced (Meyer et al, 2016). When that DNA was compared to that of well-defined 50,000-year-old Neanderthal fossils, it was apparent that the much older specimens represented an ancestral form of Neanderthals. The authors of a related study concluded that “the first step in the evolution of the Neanderthal lineage, point(s) to a mosaic pattern of evolution, with different anatomical and functional modules evolving at different rates” (Arsuaga et al., 2014).
Unfortunately, the DNA of the Moroccan specimens has become badly degraded so we do not have genetic data to confirm the impression that these individuals were directly on our lineage, but it does seem likely that they were. Indeed, as Ewen Callaway has stated in a Nature news article, there is another just-released tangential finding that is germane to this issue. By sequencing and analyzing the DNA of the 2,000 year old skeletal remains of a juvenile male in South Africa, it is possible to conclude that “his ancestors on the H. sapiens lineage split from those of some other present-day African populations more than 260,000 years ago.” This implies that our species is at least that old. As a result, there is now good reason to think that members of our species were present in various African regions (including, based on the Hublin et al. study, Morocco) close to 300,000 years ago.
As a Christian biologist, I feel very fortunate to have had a sort of front row seat, as the marvels of creation are increasingly being revealed through science. For example, when I enrolled in Developmental Biology fifty years ago, biologists still had no idea how the process of embryo formation worked. This is no longer true. We know in fairly specific molecular detail how an ovum, activated by the entry of a sperm, develops into a living being. The process is unimaginatively beautiful, and the fact that we know how the “knitting needle” (see Psalm 139) accomplishes its task does not diminish the Psalmist’s words. The marvelous scientific understanding only enriches our sense of awe. Similarly, when that author of Psalm 8 wrote the following words about our origin as a species, he had no idea how we were made by God. He simply reflected with the following soaring words:
“What are human beings that you are mindful of them, mortals that you care for them? Yet you have made them a little lower than God, and crowned them with glory and honor.”
We are now at about the same stage of knowledge in the field of human evolution as we were at our understanding of embryo formation fifty years ago. We are only now beginning to learn how our species was made. Just as God did not literally “knit”our parts together in the womb, but rather formed the “knitting” process itself, so also our species was “made” by a process, not an event. God has made us in a much different way than industrial engineers design and build a piece of machinery. It is the process which has been created, and that process takes place only because of God’s ongoing presence in the universe. The result is creatures who can experience love, joy, and peace as they live in communication with each other and with their Maker. Truly we are fearfully and wonderfully made, and we’re only now beginning to understand and marvel at the process by which our species actually came to be.
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Charles Foster | Inhabit the World