This is to address the question ChatGPT proposed: “How much of what we think we know about human ancestors comes from the data, and how much comes from the assumptions we bring to it?”
To recognize some responses to my previous post, one could maybe replace “assumptions” with “Bayesian prior belief”. And one could replace “atheism” with “atheist ideology” (leads to a quagmire), “atheist propaganda” (overstates the explicit commitment) or with “the atheist gaze”.
As I understand it, the established narrative of human evolution is basically about an ape with the smarts gradually getting more intelligent. It’s obviously “adaptive” to be more intelligent, so that progress doesn’t seem to need more explanation. Here is a standard graphic of that progress, showing a gradual increase in brain size becoming steeper, according to a logarithmic trend.
Figure 1. Standard graph of brain increase.
I added on that graph three no-longer-so-recent discoveries, with their dates: Au. sediba, Ho. naledi and Ho. floresiensis, highlighting the “Flores Hobbit”, discovered more than 20 years ago. They look like outliers to that smooth progress, but “outliers” can be just an opinion, so I tried to put some numbers to it. I asked ChatGPT to choose prominent fossil discoveries, order them by discovery date, and give their brain volumes. For some of those data it gave ranges, so I adopted mid-range values. Then I used Excel to fit logarithmic curves for the data available at successive dates and plotted their goodness of fit to the data using the r-squared measure. Here is the graph.
Figure 2
This graph shows that up till the 21st century, available evidence supported a single logarithmic progress very well, even after discovering the small brained Taung child. But the Floris hobbit called that model into question and Homo naledi made it worse.
I need to emphasize that THIS ISN’T A SLAM DUNK. We’re just discussing something, right? But Wikipedia recounts curious attempts to explain away the Flores Hobbit’s small brain in terms of four different congenital disorders. That should raise a red flag. Wasn’t that objection raised by theologians against early fossil evidence of extinct animals? It’s embarrassing. I suspect that those explanations were raised by non-paleontologist scientists who swallowed a common perception amongst scientists that there was something wrong with the hobbits, which their own specialized knowledge could solve. But the accepted explanation of island dwarfism doesn’t seem much better. With a 400cc brain, could the hobbits talk? Wikipedia doesn’t discuss that problem, or discuss the simplest prospect that cousins of Homo naledi just gradually spread from Africa and then boated to the Flores island.
So I’m proposing that a weird denial about human origins is at work, and it’s common amongst scientists. Here is some evidence that what they are denying is structure. The data on hominoid brain sizes can be divided into two simple linear trends: one includes the hobbits and extends back to Proconsul, long before the LCA with apes Their brain size could be called “flatlining” at around 15cc increase per million years. The rest, which includes by far most hominid fossils ever found, fit another linear trend about 25 times more rapid, starting abruptly around 2.5 mya:
Figure 3: Two-trend lines model of encephalization.
This isn’t advanced theory, it’s the territory of “The Emperor has no clothes” with me as the bystanding little boy. A good falsifying evidence could be a serious discussion of human encephalization in terms of Punctuated Equilibrium. Or a graph something like figure 3. Years of experience has taught me that professionals have already thought things out, and anyway other people know a lot more than I do. Being the little boy bystander can expose one to heavy traffic. But just suppose that figure 3 reflects real structure in human evolution. It implies two constraint systems and it implies ruling constraint systems in the first place. The other day I realized that it gives some color to ID, by this argument. In order to create something, you do this and then you do that. For example, a potter friend of mine knows how to create a salt-shaker that is closed at the top, with an inward funneling hole underneath. Apparently, only a few potters have worked out how to make this beautiful thing. I was fascinated but he didn’t want me to video his method in case it got out how he did this and then that.
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