The Evolution of Cranial Capacity in Humans and Stem-Humans

(Hey, I'm actually writing on the blog's title subject today!)

Here's a chart I've been working on for a while:

This shows all known human and stem-human individuals, plotted according to stratigraphy and cranial capacity (endocranial volume). The fossil individuals with known cranial capacity are highlighted as white circles; other fossil individuals' probable capacity is inferred from these. The "chimpanzee range" shows the span between a normal female bonobo chimpanzee (Pan paniscus) and a normal male common chimpanzee (Pan troglodytes) (Begun & Kordos 2004); the full range for chimpanzees (Pan) is slightly larger (but not much). The "human range" shows where about 90% of living humans fall (Burenhult 1993). UPDATE: My mistake, it's the range of ~90% of living humans combined with the range of Upper Pleistocene humans (which is actually higher, on average).

Some notes:

Deeper Dive on the PhyloPic T-shirt

Just to review:

•  PhyloPic is a website featuring freely-reusable silhouettes of organisms. Anybody may submit images under a Creative Commons license.
• I am attempting to raise funds to host PhyloPic for the next two years by selling a PhyloPic T-shirt, depicting the past half-billion years of our evolutionary lineage with free silhouettes.

We've come a long way.

In this post I'll go into more detail about what, exactly, is on the shirt, starting with the final silhouette and going back in time. In each entry, the taxonomic name links to a page for the image, with artist and license information. Some terminology first: "concestor" means "most recent shared ancestor", and "stem-X" means "not X, but more closely related to X than to anything else alive".

The final silhouette is a modern human, Homo sapiens sapiens, specifically a Melanesian woman. Melanesians and other Oceanians represent one of the furthest migrations of humanity from our original geographical range.

Immediately behind her is another Homo sapiens sapiens, this one a Subsaharan African man. Subsaharan Africa is the wellspring of modern humanity. (This isn't meant to imply an ancestor–descendant relationship between the two figures; they're just coexisting members of the same subspecies.)

Half a Billion Years in the Making: The PhyloPic T-shirt

Yes, now you can wear PhyloPic.

The PhyloPic T-shirt

PhyloPic's silhouettes are free, but hosting the site costs money. With this shirt, I'm trying to raise enough to cover basic expenses. If 100 of you buy a shirt, you will cover PhyloPic's hosting for the next two years.

The design uses PhyloPic silhouettes to depict the evolutionary lineage of humanity, starting with the earliest bilaterian animals. All of the silhouettes are public domain, or available under a Creative Commons Attribution or Attibution-ShareAlike license (which means the design itself is under a Creative Commons Attibution-ShareAlike license). The works of ten artists are featured:

• Dmitry Bogdanov
• Steven Coombs
• Ghedoghedo
• T. Michael Keesey (myself)
• Gareth Monger
• William G. Scott (RNA enzyme on the back)
• Smokeybjb
• Brian Swartz
• Nobu Tamura
• Mateus Zica

The shirt is only available through March 15. As of this morning, 25 shirts have been purchased, meaning that we are exactly one quarter of the way to the goal. So help PhyloPic out, and get a great T-shirt! Or, if you can't*, at least help spread the word.

Do you have PhyloPic's back?

* Apologies, but shipping is only available in the U.S., Canada, and Army or Fleet Post Offices. But if this campaign does well, I'll certainly look into a more global option for future shirts. (Yes, plural. Why should Homo sapiens get all the fun? PhyloPic has good coverage of many other lineages.)