Lucy Lived in the Trees

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Posted on December 3, 2016 in Darwin and Evolution, Dumb Ideas, Early Man, Education, Human Body, Mammals, Media, Philosophy of Science

A new CT scan of Lucy’s bones show adaptations for living in the trees.

Early hominin Lucy had powerful arms from years of tree-climbing (New Scientist): “Lucy, the world famous early bipedal hominin, was a swinger,” Colin Barras writes. “Scans of her skeleton confirm that she had an exceptionally powerful upper body, thanks to spending a lot of time climbing trees.” This may be the “final word on Lucy’s lifestyle,” he says; “…Lucy had long chimp-like arms and fingers – features that would seem ideal if her life involved a great deal of tree-climbing.

Human ancestor ‘Lucy’ was a tree climber, new evidence suggests (Science Daily): This press release from the University of Texas at Austin says “analysis of special CT scans by scientists from The Johns Hopkins University and the University of Texas at Austin suggests the female hominin spent enough time in the trees that evidence of this behavior is preserved in the internal structure of her bones.” For years paleoanthropologists claimed Lucy walked upright. That view has moved recently toward a more arboreal lifestyle. “Lucy’s upper limbs were heavily built, similar to champion tree-climbing chimpanzees, supporting the idea that she spent time climbing and used her arms to pull herself up.”

Bipedal Human Ancestor ‘Lucy’ Was a Tree Climber, Too (Live Science): “High-resolution computed X-ray tomography (CT) scans of long bones in Lucy’s arms reveal internal structures suggesting that her upper limbs were built for heavy load bearing — much like chimpanzees’ arms, which they use to pull themselves up tree trunks and to swing between branches.”

The only way to maintain the missing-link status of Lucy is to keep her part of the time on the ground. Mindy Waisgerber illustrates that talking point in the Live Science article: “‘Lucy,’ an early human ancestor that lived 3 million years ago, walked on two legs,” she states forthrightly. “But while she had her feet firmly planted on the ground, her arms were reaching for the trees, a new study shows.

The results of the scan are published in PLoS One, an open-access journal where anyone can check the data. The authors say their data reinforce the view that Lucy was comfortable both on the ground and in the trees. “It is clear that A.L. 288–1 and australopiths in general show many postcranial adaptations to terrestrial bipedality and probably walked in a basically human-like manner when on the ground,” they begin, citing eight prior publications. Yet their own work shows otherwise.

However, we found that A.L. 288–1 also exhibits morphological features that imply substantial differences in locomotor behavior from that in modern humans or early Homo. Lucy’s femoral/humeral diaphyseal strength proportion indicates greater muscular loading of her upper limb relative to her lower limb than is characteristic of either modern humans or Homo erectus, and more similar to that of chimpanzees. While other behavioral explanations are conceivable (such as increased upper limb use related to food procurement or defense), given the range of morphological evidence throughout her skeleton that is consistent with greater arboreality, the most likely explanation is that Lucy climbed trees with a greater reliance on her upper extremity much more frequently than modern humans or early Homo (with the exception of H. habilis sensu stricto).

A search through the paper for actual evidence supporting adaptation for terrestrial life shows mainly suppositions and lateral passes to earlier writers. This posturing is clear in the ending Conclusions section. Remember that nobody ever witnessed Lucy walking on the ground in real life. And if she did, they admit it was probably awkward, just as it is for chimps and bonobos today who can walk upright for short periods.

Although bipedal when on the ground, the limb bone structural proportions of A.L. 288–1 provide evidence for substantially more arboreal, i.e., climbing behavior than either modern humans or Homo erectus. The frequency and magnitude of force required to stimulate bone modeling and remodeling of this kind implies that this behavior was adaptively significant and not a trivial component of the locomotor repertoire. Possible reasons for using the trees more often include foraging for food and escape from predators. Furthermore, there is evidence that terrestrial bipedal gait in A.L. 288–1 may have differed in subtle but important ways from that of later Homo, decreasing locomotor efficiency when on the ground and limiting terrestrial mobility. Overall muscular strength relative to body size was likely greater than in Homo, perhaps reflecting less reliance on technology for food procurement/processing and defense. Where possible to evaluate, the same morphological attributes are present in other australopith specimens as well as H. habilis sensu stricto, i.e., OH 62 [13]. Overall these observations imply fundamental differences in ecology and behavior between australopiths and Homo erectus. It is likely that a number of different forms of terrestrial bipedality were practiced by early hominins, and that arboreal behavior remained an important part of the locomotor repertoire in particular taxa for millions of years.

That last sentence is all supposition. What they actually found was a chimp-like climbing ape built for life in the trees. The australopiths are all ape-like; the Homo are all upright walkers with “fundamental differences in ecology and behavior.” The gap is widening, not closing.

National Geographic has crow on its plate but hasn’t eaten it yet. Now that Donald Johanson is famous as an NG hero, will he recant? Not likely. Lucy is too valuable an icon for the imaginary world they live in. Too many articles have been written. Too many TV specials have been made. Evolutionists all sing the “I Love Lucy” jingle. She must be brought down from her treetop. They pull her down and shout, “Walk, Lucy, walk!”

 

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