Thr92Ala polymorphism in the type 2 deiodinase gene: an evolutionary perspective

PURPOSE

In the past, a role of thyroid hormones in human evolution has been hypothesized. T3, the metabolically active form, derives from extrathyroidal conversion of T4 by deionidase 2 (D2) enzyme encoded by DIO2 gene. In thyroid-deficient patients, decreased levels of free T3 have been associated with the polymorphism rs225014 A/G in DIO2, which causes the substitution of Threonine with Alanine (p.Thr92Ala) at protein level.

METHODS

We compared DNA and protein sequences of D2 from archaic human subspecies with those of contemporary humans.

RESULTS

Neanderthals and Denisovans displayed only the G allele at the rs225014 polymorphism, which encodes for an Alanine on the amino acid level. These data suggest that these hominines were homozygous for the Ala amino acid. These arcaic humans often lived in condition of iodine deficiency and thus, defective mechanisms of T3 biosynthesis could be life threatining. A reduced D2 activity is likely to cause decreased T3 levels, which could be critical for those individuals. Neanderthals and Denisovans were hunters/gatherers, and their diet was mainly based on the consumption of meat, with a low intake of carbohydrates. The need for circulating T3 is reduced at such alimentary conditions. On the basis of our genome comparisons the A allele, corresponding to Threonine and associated with higher levels of circulating T3 in thyroid-deficient patients, appeared for the first time during evolution in Anatomically Modern Humans during the Upper Pleistocene and has been conserved during the Neolithic age. With the advent of agriculture and herding, individuals carrying A allele might have a higher probability for surviving and reproducing. Thus, the variant was positively selected during the evolution.

CONCLUSION

Here we present an evolutionary perspective for p.Thr92Ala variant of D2 from Neanderthals to Anatomically Modern Humans.

Early anthropogenic use of hematite on Aurignacian ivory personal ornaments from Hohle Fels and Vogelherd caves, Germany

The Aurignacian (ca. 43-35 ka) of southwestern Germany is well known for yielding some of the oldest artifacts related to symbolic behaviors, including examples of figurative art, musical instruments, and personal ornaments. Another aspect of these behaviors is the presence of numerous pieces of iron oxide (ocher); however, these are comparatively understudied, likely owing to the lack of painted artifacts from this region and time period. Several Aurignacian-aged carved ivory personal ornaments from the sites of Hohle Fels and Vogelherd contain traces of what appear to be red ocher residues. We analyzed these beads using a combination of macroanalytical and microanalytical methods, including scanning electron microscopy equipped with energy dispersive spectroscopy and Raman spectroscopy. We found that the residue is composed of the iron oxide mineral hematite (Fe₂O₃). Further analyses on associated archaeological sediments by X-ray diffraction revealed the absence of hematite and other iron oxide mineral phases, suggesting that the hematite residues were intentionally applied to the ivory personal ornaments by human agents. These findings have important implications as they represent evidence for the direct application of ocher on portable symbolic objects by early Homo sapiens in Europe. Furthermore, our results reveal shared behavioral practices from two key Aurignacian sites maintained over several millennia and illuminate aspects of pigment use and symbolic practices during a pivotal time in the cultural evolution of humans.

Oral pathological conditions of an Early Epipaleolithic human from Southwest Asia: Ohalo II H2 as a probable case of intentional dental ablation

OBJECTIVE

To describe the oral pathological conditions of Ohalo II H2, an Early Epipaleolithic human from southwest Asia.

MATERIALS

The dentognathic skeleton of Ohalo II H2 and relevant comparative data from similar chronological and/or geographic contexts.

METHODS

Gross and x-ray observations of oral pathological conditions and occlusal wear were made following published protocols. A differential diagnosis of antemortem tooth loss is provided.

RESULTS

Ohalo 2 has two carious lesions on the right M³, pulpal exposure of left M₁, and mild to moderate anterior alveolar bone loss. The right I¹ was lost antemortem, and there is probably agenesis of the left M³.

CONCLUSIONS

The pathological conditions noted are not exceptional for a Late Upper Paleolithic forager. However, the antemortem missing right I¹ is most parsimoniously explained by intentional dental ablation.

SIGNIFICANCE

Ohalo 2 could represent the oldest example of dental ablation from the Late Pleistocene circum-Mediterranean world - predating the earliest examples from both North Africa and southwest Asia by several thousand years. The similarity of the Ohalo 2 ablation pattern with later Natufians provides further evidence of potential long-term behavioral trends related to the embodiment of social identities through international body modification within the Epipaleolithic of southwest Asia.

LIMITATIONS

The pre-Natufian (∼23,000-14,500 cal BP) human fossil record is relatively sparse, making comparisons with the Natufian (∼14,500-11,500 cal BP) phases of the Epipaleolithic difficult.

SUGGESTIONS FOR FURTHER RESEARCH

Documentation of oral pathological conditions for other pre-Natufian fossils would provide greater resolution of the temporospatial patterning of oral health and embodied social identities during the Epipaleolithic of southwest Asia.