— Tool­mak­ing mon­keys

DAR­REN CURNOE is an pa­le­oan­thro­pol­o­gist with an in­sa­tiable cu­rios­ity for un­der­stand­ing the kind of crea­ture we are and how we came to be this way.

Cosmos - - Contents -

Mon­key busi­ness forces a re­think on hu­man evo­lu­tion.

WHEN DID A HU­MAN- LIKE mind first emerge, set­ting its owner on a path dis­tinct to that of other apes?

We pa­le­oan­thro­pol­o­gists have long looked to tool use as the marker – par­tic­u­larly the ap­pear­ance of a cut­ting tool known as a flake. It now seems we were wrong. Re­cent re­search pub­lished in Na­ture by a team led by To­mos Prof­fitt at the Univer­sity of Ox­ford shows that ca­puchin mon­keys reg­u­larly pro­duce sharp-edged flakes in­dis­tin­guish­able from those made by early ho­minins.

Could th­ese South Amer­i­can simi­ans be tak­ing the same first steps that even­tu­ally de­liv­ered the span­ner, wheel and smart­phone? As it turns out, no. The flakes are pro­duced by ac­ci­dent when the mon­keys smash rocks to­gether. None­the­less, the ca­puchins have thrown a span­ner in the works for ar­chae­ol­o­gists.

Since the flakes they make are not tools at all, we can no longer as­sume the flakes found in the ar­chae­o­log­i­cal record are tools ei­ther.

We know that mon­keys can make tools of other kinds, of course. Ever since Bri­tish pri­ma­tol­o­gist Jane Goodall’s pi­o­neer­ing work in the 1960s, we have known our chim­panzee cousins use tools to shell nuts and to fish for ter­mites.

Nor is tool use con­fined to pri­mates. Other mam­mals, birds, snails, oc­to­puses and even in­sects all turn out to be tool wield­ers. In fact, back in the 19th cen­tury an Amer­i­can hus­band and wife team, El­iz­a­beth and Ge­orge Peck­ham, first doc­u­mented tool use out­side hu­man be­ings. They ob­served wasps ham­mer­ing dirt with peb­bles to build their bur­rows.

Nev­er­the­less, the one tool we’ve never seen in any an­i­mal’s kit is the flake. One of ar­chae­ol­ogy’s most fa­mous cou­ples, Louis and Mary Leakey, first found flakes in the Ol­du­vai Gorge in Tan­za­nia. The arte­facts are as­so­ci­ated with Homo ha­bilis, an early hu­man an­ces­tor who lived close to 2 mil­lion years ago. H. ha­bilis made the flakes, it was be­lieved, by se­lect­ing a piece of rock – called a core – and us­ing a stone ham­mer to strike off a thin wedge. The re­sul­tant edge, sharp as sur­gi­cal steel, en­abled H. ha­bilis to butcher an­i­mals. Tell­tale cut marks on an­cient bones at­tested to their use as an­cient tools.

Ar­chae­ol­o­gists ar­gued that mak­ing a flake re­quired so­phis­ti­cated men­tal ma­chin­ery such as the abil­ity to plan and an un­der­stand­ing of the phys­i­cal prop­er­ties of raw ma­te­ri­als. This was cou­pled with uniquely hu­man hand-eye co-or­di­na­tion that, for in­stance, al­lows us to thread cot­ton through the eye of a needle.

Flake mak­ing was also thought to be as­so­ci­ated with the be­gin­nings of lan­guage, since to de­velop such a so­phis­ti­cated tech­nol­ogy im­plied in­di­vid­u­als who could com­mu­ni­cate and col­lab­o­rate, pass on knowl­edge and cre­ate cul­ture.

Now it seems that flakes per se may not rep­re­sent what we thought they did. Ca­puchins pound rocks to­gether to crack them open and lick the pow­dered quartz, prob­a­bly to ac­cess di­etary min­er­als. The process sends flakes fly­ing in ev­ery di­rec­tion. But the mon­keys don’t use the flakes as tools; they just leave them ly­ing about.

So what th­ese clever mon­keys show us is that, if we find an­cient flakes, we can no longer as­sume they were a tool made by a hu­man an­ces­tor.

The dis­cov­ery of flakes at the Lomekwi arche­o­log­i­cal site in Kenya, which dates to 3.3 mil­lion years ago, led re­searchers to pro­pose in 2015 that early hu­mans ap­peared about 700,000 years ear­lier than pre­vi­ously thought. Now, how­ever, with­out other ev­i­dence, such as cut marks on bones, we can no longer as­sume the flakes are ev­i­dence of a hu­man pres­ence.

One thing is clear: the ca­puchins have forced us to set the bar higher. A flake alone is not enough. The hunt now be­gins to find a new kind of arte­fact that is quintessen­tially hu­man in its style of man­u­fac­ture and use as a tool. Per­haps some­thing like the hand axe that we see with Homo erec­tus much later, 1.6 mil­lion years ago.

It is a very ex­cit­ing time to be an ar­chae­ol­o­gist.


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