As I am new in this forum, I am unaware of this topic having been discussed previously. But the history of possible aquatic adaptions in our species should be of interest to fellow freedivers. Here is a brief account written in a rush without spellchecking, in my second language, so I hope you are forgiving 
Some chimpanzees due to many possible scenarios (competition, fire, etc) left the african jungle and ventured out to the high grassed savannas. In contrast to life in the jungle where smaller bands were less audible and visible (and statistically less suspectible to contaigous disease), the savanna posed threat of a plethora of fast moving predators, so being aware of the surroundings became paramount. As our hairier ancestors like us primarily relied upon vision for danger detection, the individuals who could see over obstacles (ie tall grass) ran a lesser risk of ending up in a predators maw, as well as spotting prey. Hence our ancestors gradually rose to be walking on two limbs, and became specialist savanna hunters.
As hominids evolved they became increasingly less restricted to one environment. They moved between different environments to exploit the seasonal abundance of each.
Some groups of hominids lived near the coast at the same time as other groups lived inland, but coastal regions which included a savanna littoral and forested river valleys were the regions of greatest population density. Coastal hominids exploited sea foods as well as forest valley and savanna foods. They had a wider variety of foods than inland hominids, and less risk of seasonal dearth. They had a higher population density because the area needed by each group to obtain food was smaller and so they were closer together. Most hominid evolution seems to have occurred on the coast and included aquatic adaptations.
The most likely situation in which the complex hominid brain evolved was just such a complex region. A wide variety of food sources was exploited, requiring a wide variety of strategies, and providing the quantity and quality of nutrients necessary for brain growth (different fatty acids in particular).
Sir Alister *Hardy proposed the idea that hominids at some stage in their evolution were aquatic or semi-aquatic. It seemed to him that many of the differences between modern day humans and apes could be interpreted as aquatic adaptations.
Principal among these was a lack of body hair together with a layer of fat under the skin. Hair is useless for insulation in the sea in a larger mammal; a layer of sub-cutaneous fat is better. Hair impedes the free flow of water over the body; fat fills out the hollows and streamlines.
These features are found in humans and the larger aquatic mammals alike. It is argued that they developed in unrelated mammals through a process of convergent evolution.
Other possible aquatic adaptions freedivers in particular are keenly familiar with are the diving reflex, blood flow changes during anoxic conditions and increased pressure (out of the periphery), as well as the instinctive swimmin proficiency we may obsere in infants.
The study of mitochondrial DNA suggests that all humans alive today descended from a small group of people living in Africa perhaps as little as 100,000 years ago. Some recient findings suggest that they evolved on the coastline of East Africa, not the interior.
Floods and tsunamis may have been an important initial selection factor for swimming ability, most probably first influenced by individual differences in body fat (for thermoregulation and bouyancy). Gradually becoming more water proficient, and due to lack of sophisticated tools and techniques (like fishing poles), the hominids had to venture into the water and catch marine animals, hence some sort of spearfishing culture may have evolved. If these (both physiological and cultural adaptions) increased survival and thus reproduction over a long enough period of time(thousands of years), physiological adaptions to a marine environment probably occured.
If these marine hunters aquatic phenotype disposing genes were bred into and later dominated (had a higher adaptive value than other alleles) the gene pool of what would be known as homo sapiens, the adaptions would become universal human traits. Alternatively an evolutionary U-turn, with hominids moving onto the savanna, outcompeting their other previously isolated tribes found place
The "aquatic theory" has limited empirical evidence, and is viewed as "armchair speculization" by many evolutionary biologists and anthrophologists, but has gotten more attention in the latter years. Personally I find it compelling, but in lack of data. It is also in some areas not compatible with more conventional and better documented theories of hominoid evolution. Would be interesting to get a discussion going on the matter here, even if this is not an academic forum. And as a last note, please refrain from discussing the validity of evolutionary theory (bringing creationist beliefs and the like) as I (at least) would find that very uninteresting and besides the issue.
Some chimpanzees due to many possible scenarios (competition, fire, etc) left the african jungle and ventured out to the high grassed savannas. In contrast to life in the jungle where smaller bands were less audible and visible (and statistically less suspectible to contaigous disease), the savanna posed threat of a plethora of fast moving predators, so being aware of the surroundings became paramount. As our hairier ancestors like us primarily relied upon vision for danger detection, the individuals who could see over obstacles (ie tall grass) ran a lesser risk of ending up in a predators maw, as well as spotting prey. Hence our ancestors gradually rose to be walking on two limbs, and became specialist savanna hunters.
As hominids evolved they became increasingly less restricted to one environment. They moved between different environments to exploit the seasonal abundance of each.
Some groups of hominids lived near the coast at the same time as other groups lived inland, but coastal regions which included a savanna littoral and forested river valleys were the regions of greatest population density. Coastal hominids exploited sea foods as well as forest valley and savanna foods. They had a wider variety of foods than inland hominids, and less risk of seasonal dearth. They had a higher population density because the area needed by each group to obtain food was smaller and so they were closer together. Most hominid evolution seems to have occurred on the coast and included aquatic adaptations.
The most likely situation in which the complex hominid brain evolved was just such a complex region. A wide variety of food sources was exploited, requiring a wide variety of strategies, and providing the quantity and quality of nutrients necessary for brain growth (different fatty acids in particular).
Sir Alister *Hardy proposed the idea that hominids at some stage in their evolution were aquatic or semi-aquatic. It seemed to him that many of the differences between modern day humans and apes could be interpreted as aquatic adaptations.
Principal among these was a lack of body hair together with a layer of fat under the skin. Hair is useless for insulation in the sea in a larger mammal; a layer of sub-cutaneous fat is better. Hair impedes the free flow of water over the body; fat fills out the hollows and streamlines.
These features are found in humans and the larger aquatic mammals alike. It is argued that they developed in unrelated mammals through a process of convergent evolution.
Other possible aquatic adaptions freedivers in particular are keenly familiar with are the diving reflex, blood flow changes during anoxic conditions and increased pressure (out of the periphery), as well as the instinctive swimmin proficiency we may obsere in infants.
The study of mitochondrial DNA suggests that all humans alive today descended from a small group of people living in Africa perhaps as little as 100,000 years ago. Some recient findings suggest that they evolved on the coastline of East Africa, not the interior.
Floods and tsunamis may have been an important initial selection factor for swimming ability, most probably first influenced by individual differences in body fat (for thermoregulation and bouyancy). Gradually becoming more water proficient, and due to lack of sophisticated tools and techniques (like fishing poles), the hominids had to venture into the water and catch marine animals, hence some sort of spearfishing culture may have evolved. If these (both physiological and cultural adaptions) increased survival and thus reproduction over a long enough period of time(thousands of years), physiological adaptions to a marine environment probably occured.
If these marine hunters aquatic phenotype disposing genes were bred into and later dominated (had a higher adaptive value than other alleles) the gene pool of what would be known as homo sapiens, the adaptions would become universal human traits. Alternatively an evolutionary U-turn, with hominids moving onto the savanna, outcompeting their other previously isolated tribes found place
The "aquatic theory" has limited empirical evidence, and is viewed as "armchair speculization" by many evolutionary biologists and anthrophologists, but has gotten more attention in the latter years. Personally I find it compelling, but in lack of data. It is also in some areas not compatible with more conventional and better documented theories of hominoid evolution. Would be interesting to get a discussion going on the matter here, even if this is not an academic forum. And as a last note, please refrain from discussing the validity of evolutionary theory (bringing creationist beliefs and the like) as I (at least) would find that very uninteresting and besides the issue.
