2. The Evolution of Species
Darwins „On the Origin of Species” which was published in 1859, is regarded as the most important fundamental book of evolutionary biology. Evolution needs time. A perceived expansion of time with regards to the existence of the earth was crucial for Darwins insights. Until the 19th century, the age of the earth was estimated to be not older than a few thousand years based on religious texts. In the 18th century, the natural scientist Edmund Halley tried deducing the age of the earth from the salt contents of rivers and seas and concluded that the earth must be considerably older than 6000 years, but was satisfied with this notion without giving his own estimate (3). Consequently, in Darwin’s days, the age of the earth was not yet known. Independantly from external scientific doctrines Darwin must have realized himself, that the existing species on earth must have had more than 6000 years of time to develop, if his evolution-theory ought to be plausible. In “On the Origin of Species” Darwin estimated the age of the earth to around 300 million years. As we know now, 300 million years ago was the transition period from perm to carbon. The richt forest and swam flora of this period was the raw material for geological layers that we exploit in our days as coal. Among the animals of that period were amphibiae, who became more and more independent of water. Today the age of our planet ist estimated at 4.6 billion years.
Darwinism and Lamarckism
The French natural scientis Jean Baptiste de Lamarck (1744-1829) already shaped the idea of development of species. Darwin’s ideas were to some extent in the air. Alfred Russel Wallace (1823-1913) would probably also have developed the concepts that Darwin shaped in “On the Origin of Species”, if Darwin had not existed. Without any doubt, also Lamarcks ideas show a lot of agreements with Darwin. When talking about Lamarckism, it is therefore the differences that are being stressed. Lamarckism claims that properties and capabilities acquired during life can be passed on to offspring. Such an inheritance of acquired properties would in principle shorten the required time for evolution, compared to natural selection over many generations. An illustrative example for explaining the differences between Darwins and Lamarcks theory is the giraffe: Her long neck allows her to eat leaves in heights that no other plant eater of the prairie can reach. According to Lamarck giraffes of past generations would have stretched their necks again and again thus lengthening their neck during their lifetime. This lifetime-behaviour induced lengthening would then have been passed on to the next generation. According to Darwin’s views the long neck of the giraffe is not the result of passing on “training-lengthened” necks to the next generation. Rather giraffes with long necks must have had better survival- and reproduction chances and thus giraffes with long necks passed on their properties to the next generation more frequently than giraffes with a short neck. Lamarck thus postulated the inheritance of acquired “trained” properties to be the driving force of evolution. Darwin, in contrast postulated “natural selection” with different probabilities of individuals to reproduce being decisive.
What means successful in evolution?
To reduce the mechanisms of natural selection that underly evolution to “Survival of the Fittest” is not quite correct. Social Darwinism in its worst manifestations deduced a natural Right of the Stronger from this conceptual oversimplification. This was for example done by the National Socialists to “scientifically” legitimise their atrocities which they justified with the alleged superiority of their own race. Natural selection simply means that there are traits that increase the probability that the genome of an organism is passed on to the next generation completely (asexual reproduction) or 50% (sexual reproduction). These traits do not necessarily have to be traits, we commonly regard as advantageous (e.g. strength, intelligence). Decisive for evolutionary success is only the passing on of the genome to the next generation. Sometimes one hears that in evolution traits prevail that increase the chances of survival. This may often be the case, especially, wenn survival-time is associated with the number of offspring. (A seasonal breeder with yearly offspring will have more offspring, if it lives longer). In some cases, behaviours can lengthen the life of an individual however at the cost of not-reproducing. For bee drones the copulation with the bee queen is deadly as the sperm containing reproductive organs remains in the bee queen. The abdomen of the drone thus gets ripped apart and the drone dies. Drones that do not copulate live longer (until the next autumn), however they do not reproduce.
Critical are thus traits that increase the reproduction probability. “Generation-persitance of genes of the reproductively successful“ might be more appropriate than “Survival of the Fittest“. The term “Survival of the Fittest“ was coined by the English Social-philosopher Herbert Spencer (1820-1903). Spencer was the first to consequently apply Darwins insights to human societies thus being a founder of Social Darwinism.