Acheulean hand-axes
Acheulean hand axes are so named because they were first found in Saint-Acheul in France. They date to the lower Paleolithic period, approximately between 1.7 million years ago to 13,000 years ago, and have been found, predominantly in coastal, fleuval or lakeside environments throughout Africa, Asia and parts of Europe. They are more sophisticated than the earlier 'Oldowan' stone tools, and take the form of a hefty stone tool, with a smooth, heeled base, sharp thin edges and a pointed tip.

Acheulean handaxes are often found close to Homo erectus (AKA/or: ergaster, habilis) remains but would have also been used by Neanderthals and later Homo sapiens in Europe. It has been suggested that these hand axes were used for all sorts of things, such as cutting wood, butchering meat, killing animals, digging up roots, finding mates, or even having no purpose at all, other than to demonstrate the skill of their makers. Hunting, killing and butchering animals still fits in with earlier theories about Homo ancestors being fierce carnivore hunter-killers. However, according to Wikipedia:
"The kill site at Boxgrove in England is another famous Acheulean site. Up until the 1970s these kill sites, often at waterholes where animals would gather to drink, were interpreted as being where Acheulean tool users killed game, butchered their carcasses, and then discarded the tools they had used. Since the advent of zooarchaeology, which has placed greater emphasis on studying animal bones from archaeological sites, this view has changed. Many of the animals at these kill sites have been found to have been killed by other predator animals, so it is likely that humans of the period supplemented hunting with scavenging from already dead animals.[1]
What paleoanthropologists usually neglect to consider is that the majority of these tools are found located near coasts, rivers and lakes, and are usually close to ancient shell-middens, indicating that their main purpose was probably for opening shellfish.
As Gareth F. Morgan writes in his paper: "The Acheulean Hand Axe - A Toolmaker's Perspective":
"The oldest substantial shell midden so far discovered is at the Klasies River caves on the Tsitsikamma coast of South Africa, which were inhabited for some 70,000 years by the first modern humans and possibly pre-humans before that (there is some dispute) [2]. The shell midden is 20 metres deep and includes the bones of penguins and seals. Such a quantity of shells would seem to represent fairly convincing fossil evidence of a marine diet."

Location of stone “hand axes” found in England, all on or close to coasts, rivers and estuaries. [Distribution of handaxe sites in the British Museum Collection. Large circles = more than100 handaxes; medium circles = 10-100 handaxes; small circles = less than 10 handaxes.]
We have already seen how a seafood diet is essential for brain growth and it makes sense that, instead of hunting game across dusty savannahs - a theory that has now been discredited - our ancestors were eating a great deal of shellfish. As Gareth Morgan states:
"One of the most prolific sources of C4/CAM foods though is seaweed [3]. Unlike grass and sedge, which are made of tough lignin (up to 50% in sedge), cellulose and hemicellulose, seaweed is very easy to digest, having no lignin or hemicellulose at all and very little cellulose [4].
Is there any fossil evidence of early man eating seaweed? Well yes there is.
When shell middens dating from the end of the last ice age were analysed, the sample included the remains of over 4500 gastropods smaller than 2 cm. [5]. These included 18 species of mollusc that live on or in seaweeds and sea grasses.
In addition the shells in shell middens are usually intermixed with unidentifiable plant material. Fossil plant material can usually be identified by either seeds or pollen. Seaweeds, including kelp, which evolved during the Miocene era, have neither seeds nor pollen, whereas both grass and sedge produce plenty of both.
A plateful of seaweed provides all of the recommended dietary intake (RDI) of Fibre, Magnesium, Vitamin K, Manganese, Iodine, Sodium, Calcium, Folate and Potassium as well as smaller quantities of iron, copper, omega-3 and omega-6, vitamins A, C, E, phosphorus, B vitamins and choline along with some carbohydrates, protein and fat.
It may be worth noting that choline is even more essential to brain development than either omega-3 or omega-6.
Any deficiencies can easily be made up by eating clams, which are very rich in iron, copper, selenium and zinc, vitamins C and B12 and both omega-3 and omega-6 fatty acids.
Globally we continue to consume a staggering 30 million tons of seaweed in one form or another every year, along with some 15 million tons of clams and oysters (estimates vary), and every one is shucked by hand by someone with a clam knife in one hand and scars on the other."
Clearly our Homo ancestors needed a tool to help them open so many shellfish, a tool so successful that it continued to be used for nearly two million years.
"It is not easy to open a clam. The oystercatcher, using only the very tip of its fairly blunt beak and maybe its tongue, can somehow persuade a mussel to open up voluntarily, but no one knows how it does this.
The best that twenty-first century technology can offer is the clam knife.
This has a short handle, made of wood, plastic or metal, that fits the palm of the hand and a short, flat steel blade with a very sharp point to insert between top and bottom shells of the clam, known as valves and, if you’re lucky, a cross guard as well to stop you stabbing your thumb onto the edge of the shell as the blade goes in.

It is of course quite difficult to insert the tip of the blade into the watertight seal between the two valves and it requires considerable force as the clam has a hard shell and very powerful muscles holding it closed. Consequently the clam knife is usually sold with a chain mail glove that you can wear on the other hand to keep stabbing injuries to a minimum.
How could we improve on this design?
Suppose we could chop a notch in the edge of the shell; a notch wide enough to insert the tip of an instrument to lever the shells apart. To do this we would need something quite heavy to be able to apply enough force without too much effort – say three or four hundred grams or so. It shouldn’t have a sharp edge like a knife because the notch from a sharp blade would not be wide enough to insert the lever.
Since our hands would be wet when handling clams the handgrip should not be smooth or polished or we would be sure to drop it in the water and lose it at some point.
The next tool we need is something to insert into the notch to prise the valves apart. This need not have too fine a point on it but it should be rather flattened at the tip like a screwdriver so that a quick twisting action can begin to separate the valves, and tapered so that it can then be pushed in further and a second twist will open them the rest of the way.
Ideally the notching tool and the prising tool should be incorporated into one single implement and in such a way that it is not necessary to change one’s grip between the notching action and the prising action. An Acheulian hand axe would be perfect in all respects. It makes an ideal clam shucker.
The same tool, if it has a clean edge and a slim tip, can be used with a different technique. It requires a little more speed and accuracy but saves you having to spit out bits of crushed shell from the notch. You simply bring the tool down smartly near the edge of the shell and a sliver of both upper and lower valves will shear off, leaving a clean aperture to slip the tip of your shucker into. Twist, and you’re done.
With a stone clam shucker in hand the rate of clam harvesting would have been vastly increased. Instead of returning to the shore with each one to find a rock to smash it on it would be possible to eat on the go.
Once created, the stone clam shucker design would have needed no further improvement."
Read the full paper: https://www.academia.edu/40664984/The_Acheulean_hand_axe_a_toolmakers_perspective

Map of the distribution of Middle Pleistocene (Acheulean) cleaver finds
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