Did Modern Human Faces Devolve from Those of Neanderthals?

Or are the differences
evidence of inbuilt
natural genetic variation?

 

by Jerry Bergman, PhD

When comparing Neanderthal faces with modern humans, several things stand out. One is that the entire skull of the Neanderthal is larger. Conversely, the adult human skull is closer to a child’s skull than is the adult Neanderthal skull (see figure).

As described by Professor Kristina Killgrove, “Modern humans have uniquely small and flat faces, especially compared with our Neanderthal cousins’ notoriously robust faces and large noses, but the reason for this difference has eluded paleoanthropologists.”[1]

How Faces Develop

Alexandra Schuh and her colleagues, publishing in the Journal of Human Evolution (May 2025), analyzed the midface region to compare maxillary growth and development from birth to adulthood in present-day humans (Homo sapiens; n = 128), Neanderthals (Homo neanderthalensis; n = 13), and chimpanzees (Pan troglodytes verus; n = 33). The comparisons were made by macroscopic evaluations (i.e., geometric morphometrics) and microscopic evaluations (i.e., surface histology).[2] Analysis of human individuals at various stages of their lifespan, from childhood to adulthood, charted facial ontogeny, as well as the growth and development of facial bones, and found

midfaces of present-day humans are on average already smaller at birth than those of Neanderthals and grow more slowly after birth. In particular, we find an early cessation of growth around adolescence, which is unique to our species. Microscopically, this is reflected in reduced amounts of bone resorption, indicative of decreased cellular activities linked to bone development. Greater amounts of bone formation in the infraorbital and nasal regions and faster growth rates are responsible for the large Neanderthal midface.

These results highlight the importance of postnatal ontogeny (especially in late stages) for explaining facial differences between Neanderthals and present-day humans, as well as part of the gracilization [reduction in bone mass and a trend towards slender, less robust skeletal structures] process characteristic of present-day humans.[3]

Attempts to Darwinize the Data

In an attempt to explain the differences, the authors admit that “Since their discovery, the distinct features of the Neanderthal face have sparked extensive debate, leading to various hypotheses about their evolutionary significance.”[4] These theories, actually more like guesses, include:

1. the increasingly European cold climate during the Late Pleistocene exerted selective pressures on the Neanderthal respiratory system, particularly in the nasal region;
2. the adaptation of the Neanderthal nasal morphology to cold climates, included the evolution of larger cranial airways to meet their higher energetic demands to produce more heat to keep the body at normal temperature of 98.6 degrees;
3. the enlargement of the masticatory apparatus to meet the dietary demands of colder weather;
4. the Neanderthal face evolved as an adaptation to use the incisors as tools for specific tasks such as making clothing or similar tasks;
5. the structural reorganization of the Neanderthal midface provided an advantage in resisting vertical bite forces required for chewing;
6. dietary changes, from a soft diet to a coarser diet or from a coarser diet to a softer diet, such as during the transition from a hunter-gatherer to an agricultural diet;
7. sexual selection;
8. some of the above, or even all of the above.

Bergmann’s Rule

Schuh et al. admit that “The evolution of the H. sapiens cranium is a complex process that comprises changes in size, shape, and the reduction of bony superstructures.” Although the Schuh et al.  article mentions the word evolution 56 times, a much simpler explanation is, as the authors admit, “humans exhibit the morphological adaptations in the nasal region required to withstand not only cold climates but also various other climates, expressing a high degree of plasticity. … Disentangling the contribution of population history and climate adaptation in human cranial evolution is proving complex.”[5]

All of the changes Schuh et al. highlighted, have nothing to do with human evolution from a common ancestor, but are simply examples of the enormous variety built into humanity, and, to some degree, all of life. They are simply additional examples of Bergmann’s (no relation to me) and Allen’s rule that I studied in my anthropology classes almost half a century ago. These rules help us to understand (or help to explain) the thermoregulation system required to maintain a stable body temperature.

The two “rules” used to explain this adaptation mechanism are Bergmann’s Rule, which focuses on overall body size, and Allen’s Rule, which focuses on appendage length (legs, arms, and ears). Bergmann’s Rule states that, in colder climates individuals within a species tend to be physically larger, and more robust, than those in warmer climates. The reason is larger animals not only have more fat and/or more muscle to keep in the heat, but also have a lower surface area to volume ratio.

The result is that animals in this cold environment lose less heat relative to their body size. Consequently, the more robust build is better suited to colder environments. Allen’s Rule states that animals in colder climates tend to have shorter appendages that lose less heat from their limbs compared to those in warmer climates. For this reason, limbs, ears, and tails are shorter in colder climates and longer in warmer climates to enable them to lose more heat. Examples include polar bears, which are much fatter and larger in colder regions, and sun bears, which are comparatively smaller in warmer regions (see illustrations above).

Summary

The differences discussed in the Schuh et al. paper are likely a result of the normal variations required to help different life-forms adapt to local conditions. The example given in some detail to illustrate this adaptation was the centuries old Bergmann’s/Allen’s rule, but many other examples of Bergmann’s/Allen’s rule could be used to illustrate this well-documented principle as well. The underlying genetic mechanism is not well understood and likely is related to epigenetics or some other system which affects the regulation of genetic expression or non-expression.

References

[1] Killgrove, Kristina, “Why modern humans have smaller faces than Neanderthals and chimpanzees,” Live Science, https://www.livescience.com/archaeology/why-modern-humans-have-smaller-faces-than-neanderthals-and-chimpanzees, 2025. Emphasis added.

[2] Schuh, Alexandra, et al., “Human midfacial growth pattern differs from that of Neanderthals and chimpanzees,” Journal of Human Evolution 202, May 2025.

[3] Schuh, Alexandra, et al.,

[4] Schuh, Alexandra, et al., 2025. Emphasis added.

[5] Schuh, Alexandra et al., 2025.

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Dr. Jerry Bergman has taught biology, genetics, chemistry, biochemistry, anthropology, geology, and microbiology for over 40 years at several colleges and universities including Bowling Green State University, Medical College of Ohio where he was a research associate in experimental pathology, and The University of Toledo. He is a graduate of the Medical College of Ohio, Wayne State University in Detroit, the University of Toledo, and Bowling Green State University. He has over 1,900 publications in 14 languages and 40 books and monographs. His books and textbooks that include chapters that he authored are in over 1,800 college libraries in 27 countries. So far over 80,000 copies of the 60 books and monographs that he has authored or co-authored are in print. For more articles by Dr Bergman, see his Author Profile.