Research into our ancestors has revealed that many members of the human family are “mosaic” species. In other words they contain a combination of archaic (old) and derived (newer) traits. They’re the very “transitional” forms creationists keep asking for as proof of evolution. Since these mosaic fossils stand in stark contrast to the creationist worldview most choose to ignore them. However, the good folks at creation.com have finally come up with a way to explain away these mosaic fossils. The issue is that their explanation only works if they lie about key aspects of these fossils’ anatomy.
However, deception isn’t a new tactic to explain away mosaic fossils. Earlier efforts simply omitted either the archaic or derived traits in an effort to make the species seem like one or the other. For instance, the paper which describes one of the earliest members of the human family – Ardipithecus ramidus – notes that:
The arm displays a mosaic of characters usually attributed to hominids and/or great apes. From proximal to distal, probable derived characteristics shared with other hominids include . . . [a bunch of boring anatomical features] . . .The specimen also shows a host of characters usually associated with modern apes, including . . . [yet more boring anatomical features] . . .
However, when the creationist book The Truth about Human Origins describes the fossil they selectively quote this paper; focusing only on that bold section to say
The authors of the paper in Nature described the cranial fossils as “strikingly chimpanzee-like in morphology”. The pieces of arm bone were described as exhibiting “a host of characters usually associated with modern apes”.
Therefore it totally isn’t mosaic and thus transitional! Definitely not proof of evolution. I’ve written about this example (and others) before if you’re interested in these arguments.
Creation.com present a new argument to try and explain away these mosaic fossils. However, it isn’t much more honest than simply ignoring key aspects of their anatomy to hide their true mosaic nature. To demonstrate their new argument they examine mudskippers, before applying this reasoning to mosaic fossils as well:
Mudskippers are unique mosaic creatures, not transitional forms. This means that, while they have some traits fish have, and other traits amphibians have, they are all fully formed traits . . . If evolution were true, we would expect to see a half-fin-half-leg. Instead we see a functional fin
However, this argument rests on a false claim: the notion that the traits present in these mosaic fossils are either completely archaic or completely derived. As they later write “even where it might appear to be so, on closer inspection such ‘intermediate features’ are usually readily identifiable one way or another“.
Much like earlier attempts to describe mosaic fossils as completely one way or the other; this is simply false. Whilst many mosaic species do possess traits more derived than their ancestors, they’re rarely fully modern (until we get relatively close to the present). Whilst more modern than they’re ancestors, they’re often not all the way there yet. In other words, it’s the “intermediate features” creation.com claim don’t exist.
As a case study take a look at your derived, modern hand. It has a relatively thick, long thumb. This makes it easier to pinch stuff between your fingers, handy for making tools. Speaking of fingers, they’re relatively short and stubby. Again, to make it easier for the thumb to touch them up. The archaic hand present in apes features a relatively short, weak thumb and long curved fingers. These are better suited for hooking onto branches and swinging through the trees.
Now, other members of the human family have mosaic hands. That is, hands with some chimp-like and some human-like features. Our thick thumb appears to have evolved before the fingers changed, leading to some species with derived thumbs but archaic fingers. Yet unlike what creation.com claim, the mosaic features in these hominin hands were not all the way at one extreme or the other.
Australopithecus afarensis – the species the famous Lucy fossil belongs to – has archaic curved fingers. However, they’re not as thick and strong as those seen in chimps. Hardly completely archaic. Meanwhile the more recent Australopithecus sediba has archaic fingers, but they’re significantly less curved than that seen in apes. And their thumb is more derived, but still falls outside the modern range of human variation.
This sort of pattern emerges when you examine almost any of these mosaic fossils. Returning to Lucy, she’s mosaic in the sense that she has modern bipedal capability with a chimp-like upper limbs and head. Yet even her bipedal, human-like shin still has a distinctly chimp-like curved joint with the thigh. Or the recently discovered Homo naledi, which has an archaic skull with a distinctly non-archaic occipital bun.
The list of these characteristics goes on, but hopefully I’ve made my point so I don’t have to keep boring you with nitty gritty anatomical details. Mosaic fossils do contain mixtures of archaic and derived traits, yet they’re rarely completely archaic or derived. Creation.com is simply lying when it claims they are; obfuscating the fact that these provide excellent evidence of evolution.
Kimbel, W. H., & Delezene, L. K. (2009). “Lucy” redux: A review of research on Australopithecus afarensis. American journal of physical anthropology,140(S49), 2-48.
Kivell, T. L., Kibii, J. M., Churchill, S. E., Schmid, P., & Berger, L. R. (2011). Australopithecus sediba hand demonstrates mosaic evolution of locomotor and manipulative abilities. Science, 333(6048), 1411-1417.
Kivell, T. L. (2015). Evidence in hand: recent discoveries and the early evolution of human manual manipulation. Phil. Trans. R. Soc. B, 370(1682), 20150105.
Stringer, C. (2015). The many mysteries of Homo naledi. eLife, 4, e10627.