I agree with much of the AAT, but see it as part of life in a generalised coastal tropical habitat. Your mention of occupational specialization in later humans fits with my interpretation of butted hand axes as both butchering tools and woodcrafting tools used to construct the first dugout boats from hollow bent trees at waterside. These dugouts were the ‘first cargo pickup trucks on the aquatic superhighway” that allowed trade and settlements upstream inland in areas formerly dominated by the big cat predators, and allowed relatively safe easy transport of people including babies, with slingstone pebbles as ballast in the bottom for stability, and push-pole thrusting spears propelling and spare throwing spears bunched aside like arrows in a quiver. Further development of boats included thinner lighter dugouts and later portageable ribbed skin kayaks, birchbark canoes and plank sailboats on the sea of galilee 20,000 years ago.

The words Tectonic, Technical, Technology has the root Tek, which is Greek for carpenter or craftsman. I think it derived from the sound of stone “tick-ticking” against stone to make a hand axe and other simple tools. Other languages around the world have similar sounding words for crafting tools, which suggest great antiquity. (Chip or chop are other variations of it.)

The hand in primates (and even more in anthropoids) was selected for plucking loosely hanging fruits in angiosperm trees, which had previously been the long held domain of fruit bats and frugivorous birds. Plucking allowed the changes in the jaws and dental structure, which allowed the brain to enlarge later.

This combined with greater vertical climbing and posture produced a more stable bipedal locomotion, as seen in the gibbon and spider monkey. Bipedal wading doesn’t cause dry land bipedalism (see wetland apes which wade on 2 legs but walk on 4, while gibbons are bipedal on the ground but never wade), but it does reinforce an already bipedal habit.

Most likely the combination of fruit tree climbing, wading for molluscs in mangroves, shore cliff climbing for seabird eggs, coconut palm climbing, beachcombing for turtle eggs, vertical floating (with inflated laryngeal air sac) while plucking aquatic vegetation all combined to further the upright stance in hominoids and resulted in the complete loss of the tail. Later, the ancestors of the Great apes expanded inland along gallery forests staying arboreal and becoming more quadrupedal when on the ground, while ancient Homo erectus improved swimming and changed from vertical floating to horizontal backfloating (losing the lar. throat air sac but gaining a layer of skin fat) resulting in greater hydrodynamic linearity, thermoinsulation and oxygen breath holding abilities and becoming a more adept diver for shellfish and crustaceans.

I envision them diving as male-female pairs alternating dives, while the younger males acted as area patrol guards/gangs and younger females as babysitters at the shore. Later the use of hollow logs and driftwood as floats in waters with crocs or sharks began the emergence of the most primitive vehicular industry, shells pebbles and stone tools used to make simple dugouts.