Where did it start ?

The question arises, where and when possible started forced beach combing, where early ancestors of Homo sapiens - Homo litoreus - were forced to adapt to water for food and transport...

Through an evolutionary bottleneck that forced adaptation to a in - and - out of the water life stile,
transforming them into the "swimming, singing and killing ape" he is today.

Recent DNA analyses show that the H. sapiens group started as a very small group. The genetic variation within the billions of humans of today are smaller than in the streatend leftover populations of chimpanzee and bonobo, our closest relatives (1). We have one chromosome less than they have: two chimpanzee / bonobo chromosomes conjugated in humans (2.), a possible needed source for enhancing of adaptation speed. Ad to this the recently rediscovered influences of epigenesis (3.) and rapid transformation of pre sapiens bands into sapiens becomes plausible .Geographic distribution of DNA differences point to the North East of the African continent as the most probable starting point of the human odyssey over the globe (4., 5.)

For the Homo litoreus option, the coastal areas bordering the Indian Ocean and the estuaries of rivers flowing into it are an obvious possibility. some point to the Danakil alps in the horn of africa, as these mountains were isolated islands in an archipelago in periods with high sea levels and the developing African rift valley..
The American Neurobiologist William Calvin mentions this possibility in his book on evolution, " The River that runs Uphill. " It is also possible, that the first wading "steps" of human predecessors were taken in the area between Eurasia and the Indian Plate. The Indian Plate pushed the seabed northward, resulting in an archipelago of islands between 10 and 5 mln years ago. Eventually this whole area was crushed in the collision of the Indian Plate with the Eurasian continent, ending up as part of the Himalayas. 

The process 5 miljon years ago (roughly)

The chances of recovering fossil evidence of this possible route to bipedalism of an very early semi aquatic human ancestor in this area seem dim, crumbled as they would be in the distorted sediments.
A suggestion can be that it did start during the (long) collission period between the indian continent and eurasia, with the Himalayas as enormous inheritance
This idea is  an "Out of Tibet" theory. Apart from the statements on human ancestry, it gives information about an interesting part of the geological history of our planet.

Adaptatation process in archipelago © Dirk Meijers (click)

The adaptive driving force hypothesis is based on a central view; that our ancestors at a given moment in the past were being forced in an archipelago to gather food wading, swimming and diving in shallow to moderate deep coastal waters. And not only feeding, but also mating, giving birth, playing and vocalizing. A lot of physiological pecularities of ouselves like skinfat, sebum and "nakedness" could be connected. This is shown espacially of newborns but also adolecent H. sapiens.
Possibly trapped on remote islands during periods with high sea levels, islands with very limited terrestrial resources is what we propose.
This would lead to a very high adaptive pressure on the small populations. With an upright position and stronger legs from the adopted wading and swimming lifestyle, these groups could easily disperse after a drop in sea levels. Following coastlines and riversides, this could very well have resulted started their worldwide walkabout. Add to this the plentiful presence of driftwood, rafting over greater distances for these 'amphibious' pre humans seems a logical step.

The process of isolation during periods with high sea levels, adaptive pressure towards an aquatic lifestyle, spreading out when sea levels dropped again, could have happened several times in different parts of the East Africa - Indian Ocean - Malaysian Archipelago triangle. In this view, walking, running and hunting in terrestrial environments is a secondary (but not totally) 'back to the land' process.The relatively rapid dispersion of modern man can be explained in this way. It is my speculation that this was accelerated by a nasty spin off from a strong territorial "xenophobial" nature in the then small bands of people: an inborn 'xenophobia' leading to constant neverending 'Kain and Abel' type conflicts. Moving to the next stretch of the coast or to another island to get away from hostile relatives would be the result (and it still is).

As stated, it is possible that the scenario enfolded here repeated itself. First for a prime ancestor group or groups  ofAustralopithecus spec. An long adaptive process of surviving different precursors endit with our Genus Homo  and in us  H. sapiens as far it will hold his  - including  self - destructive activities..
In his case, the high adaptive forces were not only exerted on fusil and anatomical traits, but on their 'toolbox' as well. Once freed from their island, this pressure cooker effect and their mentioned very territorial, tribal nature kick started our dispersal over the globe (and beyond).
This is for a great part rather speculative , but certainly a lot more plausible than the savanna theory.

A documented review of the possible influence of sea level rising and fall on pre humans is produced by geologist R. Little in his 'Inter Glacial Island Hypothesis'.
His essay is published on the web: Richard Little, The InterGlacial Island Hypothesis

For the dispersion  of  H. sapiens  more is now known. As Carl Ortwin Sauer already proposed for the Americas, there is indeed archeological proof of a Westcoast "road", findings under water by a specialised diving team and remains on islands.
 E.g. Americas ancient mariners

 Questions

1. Can you a description of 'epigenetic changes' and add two different examples of the effect in humans.

2. In what geological period(s) did the Indian Plate move towards Eurasia? How many millions of years took this process?

3. What is the 'age' of the Himalayas?

4. Where are the geologic aquatic "leftover" parts of the mentioned archipelago?

5. Search for possible very early human "bipedal and apelike" ancestors and their occurrence in this timespan.
   Check if the statements in " The Interglacial Island Hypothesis" could be correct.
   Go to http://en.wikipedia.org/wiki/Genus_Homo and The InterGlacial Island Hypothesis.

6. Critics of the island hypothesis an the Homo litoreus viewpoint state, that there is no fossil evidence to verify it.
   After taking in the information presented in this part, what statement would you choose:
   A Critics are right, there have to be fossils from coastal habitats to make it plausible.
   B You cannot decide if the proposals made here are possibly correct, you need more information.
   C It is possible that fossil remains are extremely hard to find, given the fact that the original habitats now are submerged.

References

1. Goodman, M. The genomic record of humankind's evolutionary roots. Am. J. Hum. Genet. 64, 31–39 (1999)

2. "Human chromosome 2 resulted from a fusion of two ancestral chromosomes that remained separate in the chimpanzee lineage".
The Chimpanzee Sequencing and Analysis Consortium (2005).

3. "Initial sequence of the chimpanzee genome and comparison with the human genome.". Nature 437 (7055): 69–873.

4. Randy L. Jirtle, PhD: Epigenetics a Window on Gene Dysregulation, Disease. Kuehn, JAMA.2008; 299: 1249-1250

5. "Strange Inheritance" , Emma Young in New Scientist, 12 july, 2008.

6. http://fidna.info/pmw/index.php?n=En.DNAAmpDeepAncestry

7. https://www3.nationalgeographic.com/genographic/atlas.html

8. Americas acient mariners

9. Carl Ortwin Saurer: exerpt from Land and Life