Evolution simply means change over time, just as Jean-Baptiste de Lamarck predicted. It is the extremely complex process by which living organisms change across time as traits are passed from one generation to the next. Evolutionary scientists attempt to understand the biological forces acting on ancient organisms to develop into the extraordinary and ever-changing variety of life seen on Earth today. They analyse the process by which plants and animal species branch off and become entirely new species, and how different species are related through complicated family trees that span millions of years.
The two towering figures in the science of evolution are Lamarck and Charles Darwin. Lamarck favoured a philosophical, a very French, approach to evolution. His theory proposes that the positive evolutionary changes result from changing needs or changes to the environment. Evolutionary improvements, according to Lamarck, happen because of: (1) use and disuse, and (2) inheritance of acquired traits. Use and disuse explains why entire species lose functions and organs they do not need or use and develop characteristics that are useful. The human appendix, for example, is just the vestige of an organ once useful; while the function of standing and moving with an upright posture helped our immediate forebears survive and thrive.
Inheritance of acquired traits is the aspect of Lamarckian evolution that has caused the most controversy over two centuries. The French naturalist-philosopher Lamarck believed that tiny changes in an organism could be triggered by an environmental event and that those tiny changes were passed on to subsequent generations, benefiting entire populations and creating new species. Lamarck felt there was a pattern in nature that was imposed from outside; that animals were constantly striving to be better. He believed in the idea of continuous progress: that somehow nature had arranged things so that every day in every way we improve.
Darwin was different. He was English, a pragmatist, and was not interested in seeing beyond the horizon of science. He couldn’t perceive any reason why things get better. But his influence was immense and his theory simple. He summed it up in just three words—descent with modification. Small changes occur in an organism, not as the result of an external influence, but as a purely random event. The changes that are beneficial succeed and are passed on to future generations while changes that are pointless or hazardous are stamped out. This process he described as natural selection.
Darwin got his theory of evolution pretty right. His natural selection was pivotal in the history of biological evolution. But the missing part was the deal-breaker. The missing link in Darwin’s theory of evolution was the mechanism of inheritance. And he never provided an explanation for the generation of new species, let alone that gigantic leap of evolutionary progress that sees an aquatic animal breathing with gills emerge from the water and start using lungs on dry land. And his great book, On the Origin of Species, never did explain the origin of species.
Lamarck and Darwin changed our view of the world around us—from a place that was considered static to a universe filled with change. We now know that the continents beneath our feet are moving, that the universe itself is expanding, that life is changing, that we’re evolving, that we’re descended from ancestors with apes as cousins. For all this we are grateful to them both.
Both theories of evolution had their ups and downs during the nineteenth century but with the discovery of genes in the early twentieth century a new brand of Darwinism was born. Neo-Darwinists, a band of scientists and commentators who appropriated selected bits of Darwin and combined them with relevant parts of modern genetic science, believe that a genetic change or mutation is a one-off event in one gene on one chromosome in one individual. And gradually the change spreads throughout a population to the point where everyone has it —but only if it confers an advantage on those individuals who carry the mutation. That’s Darwin’s natural selection. Mutations are a rare but slow and continuous source of new genes in a gene pool. It’s only once in a great while that a mutation provides an organism with an advantageous trait and Darwin’s natural selection then sorts out the useful changes in the gene pool. When this happens, populations evolve. Beneficial new genes quickly spread through a population because members who carry them have a greater reproductive success, or evolutionary fitness, and consequently pass the beneficial genes to more offspring. Conversely, genes that are not as good for an organism are eliminated from the population because the individuals who carry them do not survive or reproduce as well as individuals without the bad gene.
Natural selection only allows organisms to be selected for their current environment. Should environmental conditions change, new traits may prevail. In periods of prolonged cold temperatures, for example, natural selection may favour larger animals because they are better able to withstand extreme temperatures.
Lamarckians such as Australian scientist Dr Ted Steele and neo-Darwinists agree that natural selection plays a critical role in evolution. Once a beneficial mutation has occurred, natural selection favours those with the gene and it spreads rapidly and beneficially throughout a population. Where they differ is in the causes of the gene mutation.
For neo-Darwinists, only random mutations in the sex cells of an individual can make evolutionary changes. For Ted Steele and his contemporaries, changes, say environmental changes, in normal body cells during the life of the parent can pass to its sex cells (germline) to be inherited by offspring.
Modern followers of both Lamarck and Darwin agree that species do not change overnight, or even in the course of one lifetime. Neo-Darwinists believe that evolutionary change occurs in tiny, almost imperceptible increments over thousands of generations; periods that range from decades to millions of years. To study the evolutionary relationships among organisms over such long periods, scientists must perform complex detective work, deriving indirect clues from the fossil record, patterns of animal distribution, comparative anatomy, molecular biology, and finally, direct observation in laboratories and the natural environment.
Scientists like Ted Steele, unfettered by the neo-Darwinian dogma that today owes little to Darwin, believe that major environmental or anthropological events stimulate quick genetic responses resulting in new abilities in many adults simultaneously, making transmission to successive generations rapid and widespread. Lamarck’s inheritance of acquired characteristics and Darwin’s natural selection are both at work in this new Lamarckism.
Evolution is today a scientific fact of the modern world. It is all the more remarkable, therefore, that Lamarck believed in organic evolution at a time when there was little or no empirical evidence to support his belief and nor was there any theoretical framework to even explain the idea of evolution. It was, in fact, seen as heretical at the time.
Darwin + Lamarck = Meta-Lamarckism
Charles Darwin was more Lamarckian than he was neo-Darwinian. Darwin’s core evolutionary idea depended on a reasonably large repertoire of natural genetic variants of a given species pre-existing in the population prior to the ‘natural selection’ of the fittest parents to produce the next generation. Darwin did place great importance on numbers—lots of variants at the same time so population change was possible. How did this natural variation arise? Darwin considered this of major importance and hence used the Lamarckian theory of the inherited effects of organ use and disuse throughout his work. Thus, in 1868 he published his detailed theory ‘Pangenesis’ to explain the origin of genetic variations. He proposed that during a somatic, or bodily, change necessary for a particular adaptation, the body cells of the excited target organ would emit genetic material or gemmules (also termed ‘pangenes’) which were considered to be minute representations of each normal or altered bodily component. These were discharged from the active organ into the bloodstream, thus allowing them to enter the germ cells and be genetically transmitted to the next generation.
Darwin’s Pangenesis theory was prescient and would have been one of his most significant scientific achievements had it found sufficient understanding and support. Pangenesis was a detailed theory, Lamarckian in nature, intended to explain inheritance of acquired characteristics and the sort of natural variability within species that his natural selection theory required. It was his mechanism of heredity. His position on these crucial issues is not widely known however, and not part of the modern orthodoxy that has demonised Lamarck. Indeed, developments this century would have mystified if not horrified Darwin. Many neo-Darwinists, particularly in Britain, have been acutely embarrassed by Darwin’s Pangenesis speculations and have, where possible, expunged them from the scientific record. It could even be argued that they have behaved like creationists in altering the facts of history to support an ideological orthodoxy. As a consequence, many interesting acquired inheritance phenomena have been suppressed or deliberately misrepresented, even though little of that evidence directly supports Darwin’s own original Pangenesis theory. The real issue is whether a modern, well-supported Lamarckian theory can be devised, consistent with well-documented parts of modern molecular genetics, and be able to be articulated with a surviving core of Darwinian natural selection. A kind of meta-Lamarckism that combines the best of both Darwin and Lamarck.
And the neo-Darwinists? They are today described by eminent scientists and scientific historians as ‘hopelessly out of date’. Evolution has entered a new era of scientific agnosticism, freed from prejudice, bigotry and the idolatry of dogma. Lamarck has emerged intact from two centuries of doubt, adulation, criticism and hope.
As you’ll see in the book, the journey was a bumpy ride.
© 2008 – Ross Honeywill. This material is subject to strict copyright protection and no part may be used without express consent of the author/copyright owner