The Americas:

Anatomically Modern Homo Sapiens

By: Winnie Mutch

General Overview:

Anatomically Modern Homo sapiens start to emerge in populations in the Americas around 16 kya. (Pitblado pg. 3) In comparison with other geographic locations populated by Homo sapiens after the expansion out of Africa roughly 1.8 million years ago, the colonization of the Americas is most likely the latest to be populated by this newly emergent species. (Hawk pg. 3)

Besides this late emergence, the Homo sapiens of the Americas feature complex developments in culture and adaptations to the environment spanning thousands of years of inhabitation. A huge adaptation we can observe in Homo sapiens of the Americas is the transition from hunter-gathering based diets to agricultural lifestyles. Not only did this change affect social and cultural development, but it also affected the physical development of early Homo sapiens by forcing the evolution of dental crowning (Rose et al.) and low trabecular bone density (Chirchir et al.) to adapt to this new lifestyle.

(Side image of Navajo Hogan and Cornfield provided by F. A. Ames)

Defining Features:

1,300 to 1,400 cc Cranial capacity
Higher and flatter forehead, no brow ridge
Rounded cranial vault
Face beneath the braincase
Bipedalism as primary movement
Third molars (wisdom teeth)
Parabolic dental arcade
Diverse pigmentation development

Homo sapiens also notably developed agriculture, which not only affected their diet but also the evolution of their teeth and internal digestion systems. (Hawk pg. 13) In general, over the last 10,000 years Homo sapiens have experienced rapid dental and skeletal evolutions. (Hawk et. al 4)

(Side image of Mayan skeleton grave site provided by Peabody Museum of Archeology and Ethnology)

Evolutionary Tree:

Human evolution is roughly divided into three parts, starting with the origination of hominids as a whole, along with bipedal locomotion starting from about 7 million to 4 million years ago. (Hawks pg. 2) This time period is where we see a large evolution away from primate lineage while also retaining those primate-like ancestral traits with the Ardipithecus and some Australopithecus species.

The second part, spanning 4 million to roughly 1.8 million years ago, encompasses the extensive growth of the Australopithecines, which brought on not only a larger growth of derived hominid-like traits but also general geographic and dietary changes. Because of this larger change within the Australopithecines, it is theorized they are the closest genus to Homo. (Hawk pg. 3)

The last stage comes with the emergence of Homo roughly after 1.8 million years ago. Homo started to disperse out of their origins in Africa to places across the globe, which laid the groundwork for denser and more diverse populations to grow and evolve. (Hawk pg. 3)

(Image below is provided by the Smithsonian National Musuem of Natural History)

Dispersion into the Americas

While the evolution into anatomically modern Homo sapiens is vast and encompasses all early hominid species, the dispersion of the Homo sapien species is also an important aspect to look at and consider when discussing Homo sapiens of the Americas.

The suggested theory as to the peopling of the Americas came in two different waves. One dating back about 16,000 to 15,000 years ago along the Pacific Rim and Alaskan coast via watercraft travel, the other coming 1,000 years later through land travel over the Beringia and ice-free corridor. (Pitblado pg. 3)

Ideas on specific founder theories vary, with two splitting groups arguing a single-founder model, which claims a single population gave rise to the population expansion into the Americas during the Pleistocene era, or a multi-founder model, which claims more than one population contributed to the Pleistocene era of Homo sapiens in the Americas. (Pitblado pg. 9-10)

(Dispersion map provided by "Early Human Dispersals Within the Americas" published in Science)

Type Specimen and Fossil Items:

Homo sapiens do not have an official type specimen. Therefore, the Homo sapiens in the Americas also do not feature a set type specimen. To remedy this, specimens of Homo sapiens localized in the Americas have been carefully picked out to try and represent the species as best as possible

Lapa Vermelha IV Hominid 1

Nicknamed "Luzia"
Site: Minas Gerais, Brazil
Close to about 11,500 years old
Homo sapien cranium, pelvis, right femur, and right forearm
Homo sapien cranium traits include no prognathism, brow ridge, larger brain capacity, smaller dentition and thicker enamel
(James Di Loreto, & Donald H. Hurlbert, Smithsonian Institution)

Tepexpan 1

"Tepexpan Man"
Site: Tepexpan, Mexico
Roughly 4,700 years old
Found near Mammoth remains dating to 10,000 years ago
Slightly more present brow ridge, prominent jaw, tall dome, thin skull walls
(James Di Loreto, & Donald H. Hurlbert, Smithsonian Institution)
(The Science News-Letter pg. 22-23)

The La Brea Woman

Site: Rancho La Brea tar pits, Los Angeles
About 10,220 to 10,250 years old
Receding forehead, prominent chin, large cranium, prominent occipital region, little to no supraorbital ridge
Partial female skeleton, about 18-25 years at death
Only remains found in Rancho La Brea tar pits
Found with domestic dog remains, though there's little evidence they were purposefully deposited at the same time
(Krober et al. pg. 1-2)
(Fuller et al.)

Works Cited:

Rose JC, Roblee RD. Origins of dental crowding and malocclusions: an anthropological perspective. Compend Contin Educ Dent. 2009 Jun;30(5):292-300. PMID: 19514263.

H. Chirchir, T.L. Kivell, C.B. Ruff, J. Hublin, K.J. Carlson, B. Zipfel, & B.G. Richmond, Recent origin of low trabecular bone density in modern humans, Proc. Natl. Acad. Sci. U.S.A. 112 (2) 366-371, https://doi.org/10.1073/pnas.1411696112 (2015).

F. A. Ames. Navajo Hogan and Cornfield near Holbrook, Arizona. 1889. Visual Arts Legacy Collection. Artstor. https://jstor.org/stable/community.13885846.

Skeleton Sitting in Grave. n.d. Peabody Museum of Archaeology and Ethnology; Collection: Carnegie Institution of Washington. https://jstor.org/stable/community.11827631.

Hawks, John, Eric T. Wang, Gregory M. Cochran, Henry C. Harpending, and Robert K. Moyzis. “Recent Acceleration of Human Adaptive Evolution.” Proceedings of the National Academy of Sciences 104, no. 52 (December 26, 2007): 20753–58. https://doi.org/10.1073/pnas.0707650104.

Hawks, John. “HUMAN EVOLUTION.” In How Evolution Shapes Our Lives: Essays on Biology and Society, edited by Jonathan B. Losos and Richard E. Lenski, 31–45. Princeton University Press, 2016. https://doi.org/10.2307/j.ctv7h0s6j.7.

Smithsonian National Museum of Natural History “Human Family Tree | The Smithsonian Institution’s Human Origins Program.” Accessed April 1, 2025. https://humanorigins.si.edu/evidence/human-family tree.

Pitblado, Bonnie L. “A Tale of Two Migrations: Reconciling Recent Biological and Archaeological Evidence for the Pleistocene Peopling of the Americas.” Journal of Archaeological Research 19, no. 4 (2011): 327–75. http://www.jstor.org/stable/41410935.

Moreno-Mayar, J.; Vinner, L.; de Barros Damgaard, P.; de la Fuente, C.; Chan, J.; Spence, J., et al. (2018). Early human dispersals within the Americas. Science, 362(6419), eaav2621. Report #: ARTN eaav2621. http://dx.doi.org/10.1126/science.aav2621 Retrieved from https://escholarship.org/uc/item/03v4b6mr

Di Loreto, James and Hurlbert, Donald H. “Lapa Vermelha IV Hominid 1 | The Smithsonian Institution’s Human Origins Program,” January 1, 1976. https://humanorigins.si.edu/evidence/human-fossils/fossils/lapa-vermelha-iv-hominid-1.

“Tepexpan 1 | The Smithsonian Institution’s Human Origins Program,” January 1, 1947. https://humanorigins.si.edu/evidence/human-fossils/fossils/tepexpan-1.

“Tepexpan Man Is Young for His Age.” The Science News-Letter 52, no. 2 (1947): 22–23. https://doi.org/10.2307/3924284.

Kroeber, A. L. “The Rancho La Brea Skull.” American Antiquity 27, no. 3 (1962): 416–17. https://doi.org/10.2307/277805.

Fuller, B. T., Southon, J. R., Fahrni, S. M., Harris, J. M., Farrell, A. B., Takeuchi, G. T., … Taylor, R. E. (2016). Tar Trap: No Evidence of Domestic Dog Burial with “La Brea Woman.” PaleoAmerica, 2(1), 56–59. https://doi.org/10.1179/2055557115Y.0000000011

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