Imagine what a turkey might think (if a turkey could think in the way we do) and say (if a turkey could talk), to its great-grand-parent (if a long-deceased turkey could listen) about the loss of the capability of flight.
“C’mon grand-papa! C’mon grand-mama! Why were you so lazy? If you’d have kept up the exercises, maybe you’d have passed on enhanced ability, and we’d be flying still. We wouldn’t be all so heavy now. Or the ground so much of an attachment.”
For, in theory, domesticated birds like turkeys, geese and chickens should be able to fly. It’s just that they don’t. For them, it’s too much like hard work.
The aspirational young turkey could find itself in a murky scientific space. We’re talking about the ‘Lamarckian heresy’ here – which requires some clarification.
Jean-Baptiste Lamarck was a French biologist who lived from 1744 to 1829, and who proposed a dual theory of evolution which became something of a forerunner to Darwin’s. Lamarck differentiated between Le pouvoir de la vie (‘the complexifying force’) which drives organisms from simple to more complex forms, and L'influence des circonstances (the adaptive force) wherein use and disuse of organs changes the form of a species.
This ‘adaptive force’ has been described as the ‘inheritance of acquired characteristics’. Interpreted simplistically, it would say that the children of a blacksmith (to use a 18th century example) would naturally grow up to have strong arms – or that turkeys would be born without the ability to fly, if their parents didn’t.
It’s this second thing that has gotten a bad rap. Although in his famous 1859 book The Origin of Species, Darwin did give some time to the idea of ‘use and disuse inheritance’, many subsequent experiments (some a little unsettling, like keeping a generation of guinea pigs or chickens intoxicated with alcohol, or rats living in revolving environments), have debunked the idea.
Evolutionary scientists now primarily reject the Lamarckian notion of the inheritance of acquired characteristics. Something that happens to one generation does not that speedily get passed on to the next. An extreme example would be if someone loses a limb during their lifetime, this doesn’t mean their children would be born missing the same. The modern science of evolution is based more on genetic changes over time.
Though all is not all done and dusted. There remain some controversial experiments – some done as recently as 2009 – which may point to significant changes made in an animal’s environment in its adolescent phase, which change its response, that are passed on the very next generation. And other parts of Lamarck’s work did and do contribute to the science of evolution.
In the case of the irascible turkey, however, it is selective breeding by humans that has hastened its confinement to land – and not as much the fact that its ancestors were lazy.
All this is oversimplification, of course. And that’s where we’re going with this: in all things about life, nothing is a simple as it seems.