Christian news worldwide

Darwin and symbiosis

It is probable that we have all been brought up to recognise the interdependence of life on this planet.

This is one factor that underlies the continual concern expressed by naturalists about the extinction of species. It is not just that it reduces the variety of life that we appreciate so much, but threatens the balance in nature. Undoubtedly some of the claims are exaggerated, but we can understand the principle and, as Christians with a ‘creation mandate’ (Genesis 1.28), we treat the concern with respect.

Close relationships

But this close relationship between living species is very real as we start to look at specific cases. We see many examples of interdependence in the natural world. This raises an important question not just about the future survival but about the origin of these plants and animals.

If two organisms are intimately involved in this way, we have to explain how they could both originate at the same time. Evolution, for example, is a time-dependent process and there must be a time lag between parallel steps in the organisms. The question of survival of at least one must be a concern. We are in fact talking of a multitude of such cases. Could all of them survive this time gap?

Darwin’s recognition

Charles Darwin recognised this and wrote: ‘If it could be proved that any part of the structure of any one species had been formed for the exclusive good of another species, it would annihilate my theory, for such could not have been produced through natural selection’ (The Origin of Species, 1859, Masterpieces of Science edition, 1958, p.164).

Scientists recognise a range of symbiotic relationships reflecting the degree to which species have a dependence on their ‘partner’. Mutualism is the case in which both benefit from the relationship. An example of this would be mycorrhizas in which there is a highly interdependent association between soil fungi and plant roots (e.g. orchids). The host plant receives essential minerals from the fungus, which, in turn, obtains the photosynthetically derived chemicals from the plant. It is reported that 95% of flowering plants grow well only with this relationship.

Humming bird

Another fascinating relationship involves the purple-throated carib (Eulampis jugularis), a humming bird, which has a unique relationship with the flower Heliconia. The male and female species differ in their beak size and shape. The shorter, less curved male beak matches the yellow variety of the flower, whereas the longer and more curved beak of the female fits the red variety.

A further example from the plant world is that of the legumes (peas, for example). A group of bacteria called rhizobia are able to take the nitrogen from the air and ‘fix’ it chemically into a form that acts as a nutrient for the plant. Atmospheric nitrogen is chemically inert and plants cannot process it directly. Also, the bacteria cannot fix the nitrogen without the aid of the host plant.

Fish cleaning

The clownfish is an oft-quoted example of a symbiotic relationship. In this case it is between the fish and a sea anemone. The fish protects the anemone from other fish that would eat it and, in turn, the tentacles (which contain a toxic chemical that stings) of the anemone protect the clownfish from its own predators. Similarly there are the examples of the ‘fish cleaning’ relationship in which one species of fish is cleaned by another sea creature.

In the evolutionary model of origins, these and many more examples of symbiosis are seen as interdependent histories of co-evolution. The problem is demonstrating that this did indeed occur, especially over long periods of time in which either or both partners would be vulnerable while awaiting the other to undergo the necessary change. For the creationist, these represent examples of the Creator’s careful planning and add to our worship of him.

JHJP

Request Free Sample

<< November 2009 >>