One of the most intriguing arguments in support of evolution comes from biological features or structures that are suggestive of historical contingency. Since evolution involves the modification of pre-existing structures to give rise to new ones, certain constraints are imposed on the possible evolutionary pathways that may be taken. Some structures are said to retain a legacy of these constraints in their current form or configuration, and are thus understood as ‘accidents of history’ or ‘suboptimal improvisations’. For example, Richard Dawkins has been making much recently about the route taken by the recurrent laryngeal nerve in giraffes (Giraffa camelopardalis). The laryngeal nerve, which serves the larynx, originates as a branch of the vagus nerve in the neck. However, it then passes down into the chest, loops under the posterior side of the aorta, and then travels back up to the larynx – in the giraffe, a diversion of some 3 to 5 metres. Dawkins’ argument is that the laryngeal nerve takes this much-longer-than-necessary route because the giraffe evolved from short-necked ancestors.
Now as I thought about this, it occurred to me that the same hypothesis might apply even from a creationist perspective. Assuming, as many creationists do, that the created kind (or baramin) is approximately equivalent to the taxonomic rank of family, i.e. encompassing all the Giraffidae, and hypothesising, as many creationists do, that the Cenozoic sediments which contain giraffid fossils were laid down in depositional events after the global Flood, we might conclude that the fossil record of giraffids represents post-Flood intrabaraminic (‘within-kind’) diversification. Furthermore, recognising that the earliest known Cenozoic giraffids (as well as the only other living member of that family, the okapi) possess short necks, we might well infer that the ancestral giraffe on the ark was short-necked and subsequently diversified into longer-necked forms, thus giving rise to a historically contingent pathway of the laryngeal nerve.
Of course, that still leaves the question of why the recurrent laryngeal nerve takes a slightly circuitous route even in mammals with short necks, including presumably the ancestral giraffid. Perhaps there’s a functional reason, but, if so, it’s not obvious what it is (ideas on a postcard, please). Some might attribute it to the inscrutability of God’s will, but that doesn’t seem very satisfying. However, the point here is that, unless we assume species fixity, the route taken by the recurrent laryngeal nerve does not help us to discriminate between creationist and evolutionist explanations of the origin of the modern giraffe as Dawkins seems to have assumed.