(Phases I - III)
became less reliable. Meanwhile on Danakil and the other islands, Homo evolution was progressing independently.

Phase IV
It is assumed in phase four that the radiation of river apes led to a number of specializations between 3.5 and 2 mya. 
A key aspect of this phase is the climate change which seems to have befallen Africa during this time. East of the rift valley it became progressively more arid, albeit in a distinctly cyclical way with ever increasing shifts and phases in those cycles. West of the rift, it appears to have remained typically tropical, much like it is today. It is suggested that those largely bipedal wading ape species (australopith-like, if not actually australopithecines) that lived on the west side of the rift were exposed to reduced need for bipedal wading and thus adopted a kind of ex-wading form of locomotion which we know as 'knuckle-walking'. Those that lived on the more arid, east side, of the rift  paradoxically, become more exposed to aquatic locomotion as their habitats shrank back ever closer to water and became more specialised to the gallery forest habitats which were exposed to seasonal, as well as much longer term, flood-desiccation cycles.

It is proposed that increased competition for reduced habitats led to a specialisation for an increased use of fish as a source of food before 2mya. It also neatly explains how sweat cooling evolved as thermoregulatory mechanism - such a wasteful (in terms of water) method only makes sense by a copious supply of fresh water.
The AHAH model proposes that this putative species was also ancestral to Homo in addition to the separate ancestors that were still inhabiting the marine coastal niches of Danakil.
Catching fish requires guile and intelligence and it is proposed that a positive feedback loop resulted (akin to the Aiello-Wheeler expensive tissue hypothesis associating meat-eating, hunting and intelligence.) There is a body of evidence linking fishy foods to brain growth and intelligence and rather less indicating that early Homo was a hunter so it is argued here that a fishing model fits this positive feedback loop better than the hunting one.
Of course throughout this time aquatic predation, especially of crocodiles would have been a constant threat and, it is proposed, a source of strong evolutionary pressure for fast wading and swimming resulting in hair loss. This would also logically result in better strategies for coping with the threat of croc predation and it is proposed that the intelligence positive feedback loop eventually reached a threshold where these early Homo ancestors overcame and actually started predating upon the crocs. Once this major cause of death was largely removed it is proposed that there would have been a population explosion resulting in the 'Out of Africa I' phase of human evolution along coasts and rivers of Eurasia.

It is proposed that as these early Homo expanded out of Afar they  would either encounter other hominid groups (in Africa) or none whatsoever (in Eurasia). It is proposed that a degree of interbreeding would have occurred resulting in African hybrids with traits that appear more ancestral (e.g. Homo ergaster) to those found in contemporary Eurasian types (Homo erectus sensu strictu.)

Phase V
The Homo ancestors on the Afar islands had, meanwhile, according to phase V been evolving along slightly different lines for over 3 million years now.
Being exposed to a more marine habitat this putative species, termed Homo maratimus in this model (and as yet not backed up by any fossil evidence), is assumed to have become more adept at swimming and diving than their fresh-water cousins.
It is suggested that they might have evolved certain traits to cope with excessive salt such as salt sweat and tears. Traits that would eventually become 'swamped out' by other traits.
Both seaside and riverside branches of human ancestors had now been living by water for several million years and it is proposed that such environments exposing individuals to the risk of drowning would naturally lead to traits to aid buoyancy including a large increase in sub-cutaneous (sc) fat, especially in infants.
The AHAH, rather controversially, claims that hominid brain growth is largely a function of the same process. It is suggested that buoyancy in infants is likely to be selected for in a species that lived in waterside niches which was not particularly adept at swimming. If one takes that buoyancy benefit as given, it is logical that an infant would not evolve sc fat in order to increase the bouyancy of its body generally  if its head was relatively dense and became submerged. Logically the head, and specifically the face, should be the most buoyant. It is therefore proposed that the massive encephalisation seen in Homo and especially in human infants compared to apes was the result of selective pressure for increased buoyancy and survivability in waterside habitats. At the very least, it is suggested, it was a side effect of increased buoyancy. 
It is proposed that this sc fat (and hence brain growth) was more pronounced in the riversiders than the seasiders due to the difference in specific gravity between fresh and sea water. Phase V ends as some geological event (probably the onset of a new ice age) caused sea levels to drop sufficiently for the Afar islands to become rejoined to the mainland.

Phase VI
The sixth phase of the AHAH begins with the proposed speciation event for Homo sapiens around 300,000 years ago. This is a second controversial idea in the AHAH. It proposes that two ancestral hominid lines - the riversiders and the seasiders - separated for about 3.5 my, now come together and interbred.

It is proposed that the resulting hybridisation lead to a peculiar set of events including the telomeric fusion of two ancestral chromosomes and a reduction in chromosomes from the ancestral 48 to the modern 46.
It is suggested that the resultant nascent Homo sapiens would be rapidly and almost totally genetically isolated from their parental groups and simultaneously benefit from a far greater gene pool from which rapid evolution might be predicted to result.
It is proposed that major elements of modern humans arose at this time including fully symbolic language and culture.
It is suggested that Homo sapiens first inhabited a hybrid zone - a kind of half-way house between marine and fresh waterside habitats - probably the estuaries around the then inland sea of Afar. But as the selective advantage of human language and culture started to surface the model proposes that human numbers began to expand at the expense of surrounding, incumbent H. erectus (Riversider) populations.

Phase VII
This phase, which I like to call (rather dramatically) "The End of Aquafaria" signifies the end of what might be called the "more aquatic phase" of our evolution. It is based on the fact that the inland sea of Afar finally evaporated away at exactly the same time that the first fossil evidence for fully modern Homo sapiens begins to appear.
It is proposed that as the sea began to dry away many waves of humans would, through increasing competition for scarcer food resources decide to leave Afar and search for a new life out across the African mainland. This process could have been going on for a as long as 100,000 years whilst other humans still inhabited the Afar sea's coastal habitats and thus maintained their largely unchanged swimming/diving lifestyle.
Eventually as the Afar sea became more hostile - increasing salination would have made it inhabitable long before it finally disappeared around 40,000 ya - almost all human populations left. It is proposed that some followed the Awash river up stream to the Ethiopian plateau. The source of the Awash is just a matter of a few kilometres from the source of the Nile. Others probably chose coastal routes.
Either way, the last human diaspora had begun and this new, talking, planning, cultured ape - incapable of interbreeding with their cousins would naturally have replaced them very quickly wherever they were encountered. 

Phases VIII - X
The rest of the story line follows the replacement model of Stringer's Out of Africa II. A radiation of modern Homo sapiens into different niches included such diverse habitats as mountains, polar regions and even dry, arid savannah grasslands.