Neuquensaurus australis
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Evolution works only with whatever variation happens to be available at the time, favouring traits that improve reproductive success in the short term. Unlike the imaginary “intelligent designer” of creationist fantasy, evolution has no foresight, no long-term plan, and no concern for what happens once reproduction has been achieved. The result is not elegant perfection, but a patchwork of compromises that work well enough for long enough.
That is why nature is full of structures and processes that serve an immediate purpose while carrying harmful longer-term consequences. Ageing itself is one obvious example, as damage accumulates, repair systems falter, and tissues and organs gradually fail. Cancers and degenerative diseases are others, arising when biological control mechanisms begin to malfunction. A genuinely intelligent designer would have no excuse for such shoddy, failure-prone systems; evolution, by contrast, explains them perfectly.
In humans, physical and reproductive fitness generally peaks in early adulthood, then declines steadily with age, until the very old, if they live that long, may become frail and dependent. From an evolutionary perspective, this makes perfect sense: once genes have been passed on, natural selection becomes progressively less effective at eliminating traits that cause harm later in life. What looks like incompetence from a design perspective is exactly what we should expect from an undirected evolutionary process.
And this is not some recent peculiarity of human biology, but a deep feature of evolution itself. A recent study by researchers from Brazil, Germany and Argentina illustrates the point with two South American sauropod dinosaurs, the Brazilian Uberabatitan and the Argentinean Neuquensaurus. These giant herbivores could apparently rear up on their hind limbs to reach high foliage, and perhaps also gain advantages in defence or display. But that ability came at a cost. As body size increased, so did the mechanical stress on the femur, making the posture progressively more difficult to sustain. In other words, evolution had produced a useful adaptation, but not a perfect one. The benefit came with a built-in structural penalty.
The researchers reached this conclusion by applying computational techniques from mechanical engineering to digital models of sauropod femurs, calculating the stresses imposed by gravity and increasing body mass when the animals reared up. Their results are published, open access, in the journal of the Palaeontological Society, Palaeontology.
