Chief Science Correspondent
Until recently, Jean-Baptiste Lamarck was the laughingstock of evolutionary biology.
However, a paper published this month in Science provides growing support for the argument that the 18th-century French biologist might not have been so wrong after all.
Lamarck proposed an evolutionary theory known as the "Inheritance of Acquired Characteristics." Essentially, an organism’s behavior during its lifetime could change certain physical traits. Those traits would then be passed onto the organism’s progeny.
When a giraffe strains its neck higher to reach a tree branch, the neck would become permanently stretched. As a result, giraffes are born with longer and longer necks as generations pass.
Today we traditionally think of macroevolution as the result of natural selection, in which the individuals most suited to their environments inherently produce the greatest number of offspring, indirectly passing on those favorable traits.
But it turns out that it's not that simple.
These changes occur during an individual's lifetime, often as a result of behavior, diet and the external environment. Epigenetic changes have been demonstrated to often persist between two or more generations in a variety of studies. However, it was not previously known if these epigenetic modifications could prompt large-scale evolutionary change within a species.
In the Science paper, a team of scientists from Israel, Germany and Spain reported epigenetic differences between the Neandertal and the Denisovan, two extinct hominin species that share a close phylogenic relationship with Homo sapiens.
The team found that that genes that had not varied between these species were actually impacted on an epigenetic scale. Essentially, some of the backbone of the genome remained unchanged, but was physically restructured so that the expression of this genome was altered - effectively creating a new species.
In the technical sense, Lamarck was still incorrect. Giraffes don't have longer necks because their grandparents stretched their own. Liza Minelli isn't a talented singer because her mother primed her own vocal chords singing "Somewhere Over the Rainbow." It turns out that life just doesn't work like that. And so that's why Lamarck's fundamental theory went unaccepted for so long. Lamarck didn't know about molecular biology, so he couldn't provide substantial evidence for his ideas.
Lamarck was correct in that individuals can control the phenotypic outlook of future generations through their behavior, even potentially creating a new species over many generations. These changes from our ancient relatives have fueled much of our neural development that makes us "human."
According to the study, of the genes that showed an altered expression were associated with brain activity and development. It also appears that many human neurological disorders - such as Alzheimer's Disease, autism and schizophrenia, may have developed as a result of epigenetic modifications on these genes.
So what does this mean for human health? Although epigenetics clearly persists through generations, it is reversible. A growing mass of evidence suggests that histone modifications are reversible. A drug that targets epigenetic alterations could potentially alleviate the up-regulated or down-regulated gene expression that prompts the development of epigenetic-associated diseases.
Perhaps a look into our ancient past will yield answers that not only show how connected we remain to our phylogenetic roots, but with information on how to improve our own future.