Jean Baptiste Lamarck: Inheritance ofAcquired CharacteristicDuringthe year 1809, when Charles Darwin was born, Jean Baptiste Lamark published thetheory of Inheritance of Acquired Characteristics. This theory was based onproposed ideas by ancient scholars such as Aristotle and Hippocrates. Lamarkendorsed his theory after noticing several lines of descent when comparing formswith existing species. He came up with the hypothesis that physiologicalchanges acquired during the life of an organism can be transmitted to theoffspring. However, according to Burkhardt, Lamark did not give much attentiontowards conducting an actual experiment to support his theory.
Instead, hebased it on a thought experiment. He provided the case of two infants who aremasked on the left eye for the rest of their lives after birth. He argued that ifthe two infants would be treated equally then joined together in future, it ispossible that with generations of similar treatment, the left eye wouldgradually disappear and the right eye begin to shift position towards thecenter of the face. In addition, Lamark also used the illustration of giraffesand argued that the generations of giraffes with long necks came about as aresult of continued stretching by the prior generations in efforts to feed fromtall trees.
Lamarkdrew implications that the phenotypic characteristics could be geneticallyacquired. In addition, he implied that for such characteristics to be transmittedto future generations through sexual reproduction, they have to be possessed byboth parents. The scientist also allowed that if parents had not been equallymodified, a character that had been acquired by one parent might at least bepartially transmitted to the offspring.
However, bearing in mind that Lamarkrelied on thought experiment to support his theory, the only test procedures thatwere relied upon were the observation of differences between existing species andorganic forms as well as compliance of the theory with conventional knowledgethat had been shared by ancient and re-known scholars such as Hippocrates andAristotle.Analysisof Lamark’s hypothesis in terms of adequacy shows that it is adequate. This isbecause of the fact that the hypothesis explains all the relevant data. First, Lamarkmade it clear that for the physiological characteristics to be passed on throughgenerations, the parents must have acquired them over time. In addition, thescientists also explained that transmission of the physiologicalcharacteristics is a gradual process which is triggered by environmentalfactors. In this case, Lamark provided enough relevant data which is supportedby generational observations to render his hypothesis adequate. Moreover, Lamark’shypothesis can also be considered to be internally coherent.
This is because ofthe fact that its components are rationally interconnected, and it does notinvolve any contradictory clauses. The hypothesis is purely based on gradual changesin phenotypic characteristics as a result environmental factors. It does not drawreference to any other elements beyond generational transmission of phenotypiccharacteristics hence avoiding contradictory information which would otherwise drawits focus out of context. However,Lamark’s hypothesis can be termed as externally inconsistent because it goesagainst other scientifically proven studies in epigenetic and transgenerationalepigenetic that have yield to different findings. For instance, a study thatwas conducted by Heijmans in the year 2008 on people born during the Dutchfamine of 1944 revealed that although adults who were conceived during thefamine had distinct epigenetic marks that their siblings born before and afterthe famine lacked, the changes could not be entirely associated withtransgenerational epigenetic inheritance. The study found out that the adultsconceived during the famine had experienced reduced production of growth factor2 (IGF2) which affected their growth unlike their siblings born after andbefore the famine.
The researchers pointed out that such changes could haveoccurred due to utero modifications rather than germline inheritance. Inaddition, the Weismann Barrier scientifically proven theory which made it clearthat germline cells contain information which is passed to successivegenerations independent of somatic cells and unaffected by experience refutedthe claims of Lamark’s theory that acquired characters could be transmittedfrom parent to the offspring. Therefore, bearing in mind that Lamark’s theorywas never experimentally proven, the scientifically proven studies managed tochallenge its misguided conventional belief.
Despitethe external inconsistency of Lamark’s hypothesis, it can be considered to befruitful. This is because of the fact that it guided scientists such as CharlesDarwin to come up with the Natural Selection theory which borrows from its ideaof use and disuse as well as transmission of acquired phenotypic charactersfrom parent to offspring. In addition, the hypothesis provided furtherdirections for application from the mere study of organisms in biology to applicationsin agriculture as proposed in the 1930s to advance service to Sovietagriculture by Trofim Lysenko who was the then President of the Soviet Academyof Agricultural Sciences.In conclusion,Lamark’s theory was based on a thought experiment which advanced the hypothesisthat acquired characters could by transmitted from parent to offspring. Thehypothesis was supported by observations of distinct features between existingspecies and organic forms. However, although the hypothesis is adequate,internally coherent and fruitful, it lacks external consistency since severalscientifically proven studies have shown different findings to the arguments ofLamark.