SF Fig. 1.6. (A) Jean-Baptiste Lamarck was a biologist from France.
Image of painting by Charles Thevenin, courtesy of materialscientist, Wikimedia Commons
Title
Practices of Science: Common Misconceptions on Evolution
NGSS Disciplinary Core Ideas
Table of Contents
Jean-Baptiste Lamarck was a French biologist and naturalist working mostly in the early 1800s (SF Fig 1.6 A). He proposed the idea that evolution was not the result of natural selection but rather the result of an individual adapting to its environment. Lamarck argued that an individual could acquire characteristics throughout its life and pass those traits on to its offspring. This type of evolution was referred to as “Lamarckian evolution” and has been widely disproven as the main mechanism for the evolution of populations. We now know that a giraffe cannot actively stretch its neck and then pass on the new, longer neck to its offspring. In a similar way, a person who loses an arm in an accident can still give birth to a child with two arms. This is because the environment (the accident) affected the person’s physical body but not the DNA they pass on to their offspring.
SF Fig. 1.6. (B) Lamarck proposed that individuals could acquire traits through will, such as a giraffe stretching its neck over time.
Image courtesy of Dan Lundburg, Wikimedia Commons
And yet, even though a giraffe can’t pass on its acquired neck traits, we do see the evolution of long necks in giraffes over time. This is because evolution occurs at the population level rather than at the individual level (as discussed earlier in the text). In a population, certain traits are favored over time, such as having a longer neck that enables a giraffe to reach more food (SF Fig 1.6 B). Having a longer neck is therefore an adaptive advantage that allows the giraffe to increase its food intake. This means a better chance of survival for those individual giraffes with longer necks, as well as increased chance of their offspring surviving.
In addition to changes in DNA that happen internally, scientists now know that there are cases where the environment can affect DNA, creating changes that are passed down from parent to offspring. Epigenetic changes are those that affect the expression of DNA rather than the DNA sequence. Epigenetic changes are also heritable, which means they can be passed down to offspring. Epigenetics is a field of biology that studies how molecules attached to DNA influence how genes are expressed in an individual.
Epigenetic changes have some similarities with the ideas of Lamarckian evolution in that changes made to adults can be inherited by their offspring. The main difference is that Lamarckian changes do not affect DNA and are not heritable, whereas epigenetic changes do affect DNA and are heritable. Epigenetic mutations have been seen in a wide variety of species, and they have been implicated in several diseases, including cancer.
