The Original question was:
Giraffe evolution – If giraffes have long necks because natural selection favoured that phenotype in an environment with high foliage, why are the adult females one metre shorter than males? Surely they would all be the same height if the evolution story were true? It is also a bit of a problem for juveniles that have been weaned. I assume that there is no evidence that the tallest giraffes offered food to the shorter ones
Answer by Diane Eager
This question is really about the power of natural selection, so let’s consider that in the context of giraffes.
The first thing to note is that giraffe survive very well in their current wild environment, but being able to survive well does not explain how they came to have the physical and functional features that make a giraffe. The presence of trees with edible leaves and fruit will not change a short necked animal into a long necked animal. It simply means that animals that are already tall enough to feed from trees will do well in this environment.
Giraffes mostly live in open woodlands and savannahs, where they browse from trees and shrubs of various heights. They feed on leaves, shoots, buds and fruits, depending on the season. Giraffes can bend their necks forward and browse from smaller shrubs and trees, as well as reach up into tall trees. The males are up to a metre (3ft) taller and can reach higher foliage, but the shorter females manage also survive quite well. It is probably just as well females are shorter than the males because the females give birth standing up, giving the new born calf a 1.8m (6ft) fall to the ground.
The much shorter young giraffes also have no problem finding food. Giraffe calves feed on their mother’s milk for up to a year, but can start to sample leaves when they are only one month old. When born they are nearly 2m (6ft) tall, and grow very rapidly in their first year, and can reach a height of 3m (10ft) tall. Therefore, when they are fully dependent on foraging young giraffes can browse from shrubs and small trees without being out-competed by other herbivores.
It’s a little known fact that giraffes can even eat grass if necessary, but they prefer not to. The grass level head down position leaves them more vulnerable to predators. The same applies when they need to drink. They go to water holes in groups, and seem to take turns in standing tall looking out for one another whilst others stoop to drink. The blood vessels in their neck are well designed with elastic, muscular walls and valves to control the flow whilst they are drinking in the head down position. This is a good reminder that it takes more than a long neck to design a giraffe.
It is also a reminder that natural selection cannot make a giraffe. Natural selection is a process where living things that are better suited to a particular environment survive at the expense of those that are not. The unsuitable ones die, while the survivors reproduce and perpetuate whatever features enabled them to survive. Natural selection explains why giraffes do well in open woodland, because their height enables to them to obtain food out of the reach of short animals. But it does not explain how it came to have these features. It only explains why each generation continues to have them.
All observations of living giraffes show that giraffes are well-designed for living in open woodlands, and in a perfect world without predators stooping down to eat grass was just as feasible as doing the same to drink, or stretching up to nibble the leaves. However, the coming of predators, especially after Noah’s Flood certainly led to a world where grass addicted giraffes were slowly eliminated leaving only the leaf nibbles who could easily see the lion coming.
Furthermore, all observed giraffes reproduce after their kind, just as Genesis tells us God created them to do. It also means there was enough room on Noah’s Ark for the baby giraffes to be accommodated on one of the floors without having to stick their necks out of the window, as usually portrayed in children’s story books about Noah’s Ark. The size specifications for the Ark would have allowed for a space of at least 5m (15ft) between two of the floors, which is plenty for the juvenile giraffes.
For more information:
DESIGN: Dawkins claims the giraffe is badly designed. How can we recognise design, good or bad? Answer here
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