Chapter abstracts, part 3:



Ch 9: "Obstetrical Implications of the Aquatic Ape Hypothesis"

Michel Odent

The aquatic ape hypothesis (AAH) offers the possibility to re-interpret several aspects of the human pre- and perinatal periods. We introduced the concept of birthing pools in the 1970s in order to treat labor pain, particularly lumbar pain in the middle of cervical dilation associated with failure to progress. We assumed that immersion in water at body temperature would be a way to reduce the level of stress hormones, facilitating the release of oxytocin. We first learned that the dilation of the cervix could progress dramatically in an aquatic environment before water immersion, and that it was associated with behavior suggestive of a reduction in neocortical control. The release of inhibitors of neocortical control in an aquatic environment was an opportunity to phrase new questions about the relationship of Homo sapiens with water. We also learned that occasionally some women did not want nor had the time to get out of the pool for the birth itself. They behaved in a way suggesting that, while in a particular state of consciousness, they knew that a birth under water was safe for the baby. The origin of this knowledge, and the strong attraction towards water that some women experience during labor, should be looked at in the light of the AAH.

By raising questions about the development of the human brain from an evolutionary perspective, the AAH enables to pose similar questions from an ontogenetic perspective. Today the focus is on the needs in iodine, docosahexaenoic acid, vitamin D, and other nutrients that are essential for brain development, and that happen to be abundant in seafood. This led us to reconsider (pre-)eclampsia as a multi-factorial syndrome, related to a maternalfetal conflict, whereby inadequate maternal nutrition is prioritized as a factor that can independently increase the probability of conflict, challenging the current belief that reduced utero-placental perfusion is the unique pathophysiological process in this human pregnancy disease. In other words, we present (pre-)eclampsia as the price some humans have to pay for having a large brain, while the specific nutritional needs are not ideally satisfied.

Other puzzling and unexplained human particularities in the perinatal period, such as human neonatal vernix caseosa and of the absence of human maternal placentophagy, can be re-interpreted in the light of the AAH.



Ch 10: "Superior Underwater Vision Shows Unexpected Adaptability of the Human Eye"

Anna Gislen and Erika Schagatay

Adaptability of the eye is a key feature in a semi-aquatic mammal and several optical and physiological strategies can be used to allow functioning of the eye in the two media, i.e., air and water. Human eyes are considered to be adapted to vision in air as more than two-thirds of the refractive power is derived from the curved cornea, an effect that is lost under water. It was observed that children of Sea Nomad groups in South East Asia appeared to have much better underwater vision than expected, allowing efficient collection of small shells from a non-contrasting background without visual aids. Studies on the visual acuity of such groups were carried out, followed by studies to reveal how the observed adaptability of the eye was achieved. Standardized optical methods were adopted to field conditions and used to reveal how the Sea Nomad children see under water. Results showed a high adaptability of the human eye to the underwater environment, with the visual acuity of the Sea Nomad children being twice that found in a European control group. Training in non-diving children was found to evoke the same adaptive responses as those observed in Sea Nomads. The mechanisms responsible for this superior underwater vision were heavy accommodation and concurrent pupil constriction, features previously observed in semi-aquatic mammals and birds. This may be an interesting example of convergent evolution. The human eye proved to be flexible and adaptable enough to function under water with an uncompromised function in air. An explanation for this surprising adaptation in a terrestrial mammal could be that it has evolved during a phase with selective pressure for foraging under water.



Ch 11: "Human Aquatic Color Vision"

Wang-Chak Chan

Many human physiological and behavioral features could possibly be explained as semi-aquatic adaptations in the remote past. However, aspects of human perception and cognition have rarely been considered in this light. In this chapter, human color vision will be discussed at two levels.

At the physiological level, visual pigments of retinal cone/rod cells, being essential to color vision, are compared among humans, their closest primate relatives, and terrestrial as well as aquatic mammals. Also the cause of human color blindness is discussed.

At the cultural level, the mystery of ‘ fuzzy’ color terms like grue (green-or-blue) in many world languages is discussed, and we propose a new model based on two arguments: each color term actually corresponds to a naturally occurring color, and the ‘ fuzzy’ terms were produced in a semi-aquatic primitive life since the dawn of human language.



Ch 12: "Seafood, Diving, Song and Speech"

Mario Vaneechoutte, Stephen Munro and Marc Verhaegen

In this paper we present comparative data, suggesting that the various elements of human speech evolved at different times, and originally had different functions. Recent work by Nishimura shows that what is commonly known as the laryngeal descent actually evolved in a mosaic way in minimally two steps: (a) a descent of the thyroid cartilage (Adam's apple) relative to the hyoid (tongue bone), a descent which is also seen in non-human hominoids, and (b) a descent of the hyoid bone relative to the palate, which is less obvious in non-human hominoids, and which is accentuated by the absence of prognathism in the short and flat human face. Comparisons with other animals suggest that (a) the first descent might be associated with loud and/or varied sound production, and that (b) the second might be part of an adaptation to eating seafoods such as shell fish, which can be sucked into the mouth and swallowed without chewing, even under water. We argue that the origin of human speech is based on different pre-adaptations that were present in human ancestors, such as (a) sound production adaptations related to the descent of the thyroid cartilage associated with the territorial calls of apes, (b) transformation of the oral and dentitional anatomy including the descent of the hyoid, associated with reduced biting and chewing, and (c) diving adaptations, leading to voluntary control of the airway entrances and voluntary breath control. Whereas chimpanzee ancestors became frugivores in tropical forests after they split from human ancestors about 5 Ma (million years ago), human ancestors became littoral omnivores. This might help explain why chimpanzees did not evolve language skills, why human language is a relatively recent phenomenon, and why it is so strongly dependent upon the availability of voluntary breath control, not seen in other hominoids, but clearly present in diving mammals.