Starchy stable isotopes? I don't think so!

Have a read at this statement from Hardy et al 2015:

“…stable isotope analyses indicate a mainly carnivorous diet for Neanderthals; a wider range of isotopic values have been observed in contemporary Middle Pleistocene H. sapiens (Richards and Trinkaus 2009), indicating that considerable differences in the levels of starch consumption existed between these two species.”

Now, if you read this I think you might be led to believe that stable isotope analysis indicates that Neanderthals were carnivores and H sapiens ate a different amount of starch to a carnivore. I feel the implication of this sentence is that H sapiens ate "more-than-zero starch" during the Middle Pleistocene.

You would believe wrongly. Did you check the reference? No? Naughty. Richards and Trinkaus (2009) actually say this:

“As the method only measures protein intake, many low-protein foods that may have been important to the diet (i.e., high caloric foods like honey, underground storage organs, and essential mineral and vitamin rich plant foods) are simply invisible to this method.”

The data do not deny starchivory. But the data equally do not in any way support its occurrence. Starch, fruit and honey are invisible on stable isotope analysis. This is a gross mis-citation of Richards and Trinkaus by Hardy et al. Never believe stuff like this without checking the refs. Easy when it is a freebie in PLOS. What do Richards and Trinkaus actually say about diets of carnivorous Neanderthals vs H sapiens? Try this:

“There are now enough isotopic data to see patterns in the data, and they show that the Neanderthals and early modern humans had similar dietary adaptations, obtaining most of their dietary protein from animals, although some of the early modern humans obtained significant amounts of their protein from aquatic, and not just terrestrial, sources.”

You can tell H sapiens ate fish because aquatic food chains are long. The longer the food chain the greater the effect visible in stable nitrogen isotopes. They make fish eating carnivores look like hyper-carnivores. That's how they show up in the paper. Had humans eaten any significant amount of protein rich plants (hazel nuts get cited as a possibility) it would show a lower stable nitrogen ratio. There is no evidence for this.

Did early humans consume starch to grow their brain size? Stop laughing! No one knows, certainly to the point where a starchivorous paper has to mis-cite a completely non-supportive paper as being actually supportive of their rubbish hypothesis.

I love it.

Did you hear the one about Jennie Brand-Miller? Passthecream linked to this gem in the comments of the last post. Some things are just too funny not to share. Have a giggle. J B-M is second author on the starch-is-needed-to-grow-brains paper...

Peter