An excellent video presentation of relative craniofacial development in humans, from birth to adulthood with comparison of male / female differences. From Beatrice Lau, University of Toronto. A basic demonstration of changes that are necessary to thinking about:
Neoteny: retention of juvenile traits in the adult animal due to some aspect of the physiological (or somatic) development of an animal being slowed or delayed. Neoteny is a factor in paedomorphosis.
Paedogenesis: reproduction by young or larval animals; the animal reaches sexual maturity while remaining otherwise immature.
Paedomorphosis: retention of juvenile characteristics in the adult animal. This includes behavior.
Heterochrony: (from the Greek hetero meaning “other” and chronos meaning “time”) describes a change in the timing of ontogenetic events between two taxa. These can be the result of relatively small genetic changes that may not even be alterations in DNA sequence, but in the timing of particular genes being expressed during development.
Examples in contemporary people: Note the developmental stages and differential growth to which these modern human faces-skulls correspond. The lower face – mandible growth lacks full adult development. The growing skull does not proceed to adult form. This is a simple visual observation of skull morphology which may indicate “feminization” of the human skull as evidence for “juvenalization- domestication” of humans during the period when we were “domesticating” specific wild animals as part of the change to agriculture; we also domesticated our species through sexual selection for tame behavior and “paedogenesis” – especially in females. It is possible that pedophilia, the pathology, is a “relic” of the selection for younger and younger, but sexually mature females.
Example below: The high domed forehead (egg-head in casual language) that has been misidentified as an indication of high (usually male) intelligence. The overall “baby-face” is common in contemporary people. “Big bulging foreheads” do not make modern humans smarter than our ancestors. Right: Neanderthal reconstruction as an example of “adult male”. Browridge, large nose and developed lower face (jaw) have nothing to do with “low, or lack of, intelligence” but a lot to do with climate, geography, diet, testosterone and lifestyle.
In western countries there is a trend toward “feminization” of males. This can occur as sexual selection by females, short-lived “fashion and fad”, or even “camouflage” of aggressive and hostile behavior. Predators in suits can play-down their criminal intent and atrocious behavior. Wall Street, The U.S. Congress, CEO’s and other political types do a great job of “hiding” their inner aggression and socio-psychopathic tendencies by looking like this:
If we were to consider the “adult” Homo sapiens skull to be presented by “archaic” forms, including Neanderthals and the AMH (anatomically modern humans) who were N’s contemporaries, (or even further back by Homo erectus!) the “developmental gap” between human varieties today and our ancestors is even more extreme.