Nina Jablonski

Jablonski studies the physiological functions of skin as well as the evolutionary and sociological influences of the past and today. Early in her skin research, she published papers on the connection between neural tube defects and ultraviolet radiation which damages folate in the skin, in the controversial and non-peer reviewed journal Medical Hypotheses.[11] She also collaborated with George Chaplin to study the pattern of melanin distribution among populations at different latitudes, discovering a correlation between skin color and the amount of ultraviolet radiation present in the individual's geographic location.[12] Jablonski and Chaplin later theorized that dark skin with sweat glands evolved with the loss of hair and sexual dimorphism in skin color (with females tending towards lighter skin than males).[13]  Jablonski's major findings explain that the physiological purpose for the variation in skin color around the world is due to the balance between the need to protect against UV radiation and facilitating the production of vitamin-D. Heightened melanin levels occur in populations closer to the equator where UV radiation poses risks of folate damage and depigmentation occurs in areas with low levels of UV radiation so that vitamin-D biosynthesis is not inhibited.[14][15][16][17]

Jablonski has taken this connection and applied it to the modernizing lifestyle. Jablonski connects certain diseases and health risks to people living in areas where their skin color is maladaptive to the environment and people who are living the modern indoors lifestyle[11]. The main diseases she found to be connected with low levels of UV-B exposure are rickets and multiple sclerosis due to inadequate production of vitamin D.[14][18] The main health problems related to too much UV radiation are cutaneous malignant melanoma, a type of skin cancer, as well as birth defects that are due to folate depletion.[14][18]

Jablonski's research on Old World monkeys is marked by extensive paleontological field work across Africa and Asia. Her work has led to significant discoveries including an ape cranium in China,[19] and the first identified chimpanzee fossils. In 2004, along with Sally McBrearty, Jablonski discovered teeth dating back to ~545,000 years ago in the Kapthurin Formation belonging to the genus Pan by comparing their measurements to those of modern Pan teeth.[20] Paleoecological evidence at the site showed that chimpanzees were not restricted to forest habitats.[21] Along with the discovery of nearby Homo fossils of the same age, this provided the first fossil evidence for spatiotemporal coexistence between the two genera.[22] More recently, Jablonski's fossil discoveries have been complemented by phylogenetic analysis of modern apes,[23] suggesting that genomic divergence in ancestral gibbons was in part due to habitat shifts during the Miocene–Pliocene transition.

Jablonski's research on the genus Theropithecus also had significant impact, including the discovery of a near-complete skeleton of T. brumpti.[24] This finding established T. brumpti as a terrestrial monkey similar to the modern T. gelada, albeit much larger. Her research is central to modern understanding of extinct Theropithecus size, habitat, and diet,[25] much of which is detailed in Theropithecus: The Rise and Fall of a Primate Genus, edited by Jablonski. She has also written textbook analyses of the fossil record of tarsiers,[26] gibbons,[27] and Cercopithecoidea as a whole.[28]

In 1994, Jablonski argued against a theory proposed by Peter Wheeler that thermoregulation played a role in hominids’ transition to bipedalism. Wheeler hypothesized that there was evolutionary pressure for early hominids to adopt bipedalism because an upright stance with less surface area exposed to sunlight allowed them to forage for longer without overheating. Jablonski's team constructed their own models, which led to the conclusion that thermoregulatory benefits weren't significant enough for natural selection to favor bipedalism.[29]

In 2014, Jablonski began researching the adaptation of goose bumps because she was interested in the connection between the integument of ring-tailed lemurs and thermoregulation. The mechanism for goose bumps is the contraction of smooth muscle called Musculi Arrectores Pilorum (MAP).[30] Jablonski noted that early primates did not have effective networks of MAP throughout the body, a factor that may have significantly affected their ability to forage under the cooler conditions of the late Eocene epoch. Using this information, she concluded that the absence of MAP networks in early primates likely contributed to their extinction in non-tropical latitudes. Jablonski also made connections between goose bumps and brain size, as the ability to regulate body temperature without changes in metabolism seemed to her a necessary adaptation to accommodate the thermal and metabolic sensitivities of larger brains.[30]

Jablonski is also interested in exploring how the behaviors of ring-tailed lemurs relate to thermoregulation. In 2016, she traveled to Madagascar where she concluded that lemurs depend on behaviors of sunbathing and huddling to retain heat.[31]