Why would long fingers evolve several times in different apes? Actually, long and highly curved fingers are known to have arisen independently in other primates as well (e.g., spider monkeys, sloth lemurs). Both show a similar degree of slight digital reduction relative to our great ape ancestor (our thumb became a bit elongated, too). Interestingly, the human hand is not that different from that of gorillas when size differences are considered. By comparison, the thumb length hasn’t changed as much. For example, whereas chimpanzees mostly elongated their metacarpals (the long bones of the palm), orangutans also elongated their phalanges (as well as their forelimb long bones). Furthermore, each of these apes achieved their current hand looks through different means. Likely, the digits became long independently in chimpanzees, orangutans, and gibbons/siamangs (in this increasing length order) from the moderate proportions reconstructed for the great ape-human and chimpanzee-human LCAs. Our results suggest that the similarities among the hands of living apes are only apparent. Our findings could surprise many: After many morphometric analyses and phylogenetically-informed comparisons, my colleagues and I found that the hand proportions of early hominins (e.g., Ardipithecus, ~4.4 Ma) are not substantially different from some fossil apes pre-dating the ape-human split (e.g., Ekembo, ~18 Ma Pierolapithecus, ~12 Ma). To understand the roots of the human hand and check if the human hand originated from a chimpanzee-like hand, we needed to compare the hand anatomy of early hominins with that of fossil apes pre-dating the times of the LCA. Over the years, I joined forces with colleagues from all over the world to have a new look at old fossils. Subsequently, the story goes that handy skills and bigger brains (associated with enhanced cognition ever more sophisticated technology) went hand-by-hand. Hence, a popular notion in human evolution is that our fingers became shorter and our thumbs longer to manipulate objects better and make stone tools. However, modern apes are better suited to move in the tree canopy. Chimpanzees (like the other living apes) can’t do it because their fingers are too long relative to their thumbs. However, living apes are more limited in their “precision grips.” Now imagine yourself throwing darts. Apes use forceful “power grips” habitually, humans too (e.g., visualize yourself using a hammer). The primate hand anatomy reflects a compromise between locomotion and manipulation. Even more, primates benefit from prehensile hands (i.e., one-hand grasping), whereas most other mammals need both hands to hold objects (imagine a squirrel chewing on a nut). For example, was the LCA a knuckle walker like chimpanzees and gorillas? Was it “suspensory,” hanging below the tree branches? Hints about the locomotion of chimpanzee-human LCA can be found in the hand of living and extinct species. Why the hand? Current debates relating to the chimpanzee-human LCA’s hand morphology are fueled by competing inferences regarding this ancestor’s locomotor repertoire. The salary was small and the working hours long, but hey, after years of internships and work as a technician, I would become a professional researcher! I was given a unique opportunity, and I wasn’t going to miss it.ĭid other aspects of the human body evolve from a chimp-like ancestor? I decided to check this idea for the case of the hand. On the other hand, my now colleagues David Alba and Salvador Moyà-Solà (my future advisor), who directed the work in Els Hostalets, invited me to study the hands of Pierolapithecus and Hispanopithecus (see cover image). That year I got lucky: On the one hand, I received a pre-doctoral fellowship from the Catalan government, allowing me to focus on research starting the following year. No doubt, the most famous fossil from the area (and likely the entire country) is the partial skeleton of the ~12 million-year-old fossil great ape Pierolapithecus. I spent 10+ hours a day working as a field paleontologist in Els Hostalets de Pierola (near Barcelona), which is well known for its amazing paleontological discoveries. At the time, I had just graduated from college. I have been researching the origins of this “uniquely” human structure since 2005.
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