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| Impending Release
of New Book:
Skin Its Natural History
In October 2006, the University of California Press will release
Nina Jablonski's new book on skin. For more information, please
visit their website at http://www.ucpress.edu/books/pages/10283.html
Fletcher Foundation Award
Dr. Nina Jablonski was awarded the Alphonse Fletcher, Sr.
Fellowship for her research, “Improving the Public Understanding
of the Biological and Social Meaning of Skin Color”.
Announced by Alphonse Fletcher, Jr., Chairman and CEO of Fletcher
Asset Management, Inc., the Fletcher Fellows include individuals
who will receive a stipend of $50,000 for work that contributes
to improving race relations in American society and furthers
the broad social goals of the U.S. Supreme Court’s Brown
v. Board of Education decision of 1954. To read more about
the Fletcher Fellowships, see http://www.fletcherphilanthropy.org/
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MAJOR PUBLICATIONS
1. Jablonski, N.G. The evolution of human
skin and skin coloration. Annu. Rev. Anthropol. 33:585-623.
2. Jablonski, N.G. and Chaplin, G. (2000)
The evolution
of human skin coloration. J. Hum. Evol. 39:57-106.
3. Jablonski, N.G. (1998) Ultraviolet light-induced
neural tube defects in amphibian larvae and their implications
for the evolution of melanized pigmentation and declines in
amphibian populations. J. Herpetology 32:455-457.
4. Chaplin, G. and Jablonski, N.G. (1998)
Comment on hemispheric difference in skin color. Am. J.
Phys. Anthrop. 107:221-224.
5. Jablonski, N.G. (1992) Sun, skin and spina
bifida: An exploration of the relationship between solar ultraviolet
radiation, skin colour and neural tube defects. In: Bruce,
N.W. (Ed.), Proceedings of the Fifth Annual Conference
of the Australasian Society for Human Biology. Perth,
Centre for Human Biology, pp. 455-462.
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KEY PUBLICATION
JABLONSKI, NINA G. AND GEORGE CHAPLIN. 2000. The evolution of
human skin coloration. Journal of Human Evolution 39(1):57-106.
ABSTRACT
Skin color is one of the most conspicuous ways in which humans
vary and has been widely used to define human races. Here we
present new evidence indicating that variations in skin color
are adaptive, and are related to the regulation of ultraviolet
(UV) radiation penetration in the integument and its direct
and indirect effects on fitness. Using remotely sensed data
on UV radiation levels, hypotheses concerning the distribution
of the skin colors of indigenous peoples relative to UV levels
were tested quantitatively in this study for the first time.
The major results of this study are: (1) skin reflectance is
strongly correlated with absolute latitude and UV radiation
levels. The highest correlation between skin reflectance and
UV levels was observed at 545 nm, near the absorption maximum
for oxyhemoglobin, suggesting that the main role of melanin
pigmentation in humans is regulation of the effects of UV radiation
on the contents of cutaneous blood vessels located in the dermis.
(2) Predicted skin reflectances deviated little from observed
values. (3) In all populations for which skin reflectance data
were available for males and females, females were found to
be lighter skinned than males. (4) The clinal gradation of skin
coloration observed among indigenous peoples is correlated with
UV radiation levels and represents a compromise solution to
the conflicting physiological requirements of photoprotection
and vitamin D synthesis.
The earliest members of the hominid lineage probably had a mostly
unpigmented or lightly pigmented integument covered with dark
black hair, similar to that of the modern chimpanzee. The evolution
of a naked, darkly pigmented integument occurred early in the
evolution of the genus Homo. A dark epidermis protected sweat
glands from UV-induced injury, thus insuring the integrity of
somatic thermoregulation. Of greater significance to individual
reproductive success was that highly melanized skin protected
against UV-induced photolysis of folate (Branda and Eaton 1978,
Science 201:625–626; Jablonski 1992, Proc. Australas.
Soc. Hum. Biol.5:455–462; 1999, Med. Hypotheses 52:581–582),
a metabolite essential for normal development of the embryonic
neural tube (Bower and Stanley, 1989, The Medical Journal of
Australia 150:613–619; Medical Research Council Vitamin
Research Group 1991, The Lancet 338:31–37) and spermatogenesis
(Cosentino et al. 1990, Proc. Natl. Acad. Sci. USA 87:1431–1435;
Mathur et al. 1977, Fertility Sterility 28:1356–1360).
As hominids migrated outside of the tropics, varying degrees
of depigmentation evolved in order to permit UVB-induced synthesis
of previtamin D3. The lighter color of female skin may be required
to permit synthesis of the relatively higher amounts of vitamin
D3 necessary during pregnancy and lactation.
Skin coloration in humans is adaptive and labile. Skin pigmentation
levels have changed more than once in human evolution. Because
of this, skin coloration is of no value in determining phylogenetic
relationships among modern human groups.
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