Mitochondria and the Meaning of Life
Written By Brianna Mattis and Dr. Justin Havird
In the Havird Lab, there is an unmistakable theme: MITOCHONDRIA. Nestled away in the quiet hallways of the Neural and Molecular Sciences Building (NMS)—replete with automated doors and the faint sounds of whirring devices—lies Dr. Justin Havird and his team. Right before his last lecture of the semester, Havird, who happens to be one of my Evolution professors, sat down with me to discuss speciation, his favorite systems, aliens, and how mitochondria may just hold the key to unlocking the meaning of life.
Before Havird was a respected researcher and professor, he was a student.
During his undergraduate years, he became interested in research and started working in a fish physiology lab. From there, he began to take interest in the genes that were responsible for the outcomes of the many “bucket experiments” he performed. As his interests in various biological fields grew, he was ultimately drawn to Dr. Nick Lane’s “Power, Sex, Suicide: Mitochondria and the Meaning of Life,” in a discussion class. And he fell in love.
As happenstance would have it, the book traced everything he loved–including the fields of ecology, phylogenetics, environmental adaptation, and molecular evolution–back to one thing: the mitochondrion. “In this book, Nick says that the acquisition of mitochondria allowed plants and animals to basically do all the cool stuff that they’re able to do,” says Havird.
Not to be deterred from exercising his professorial habits, he rises to select a dry-erase marker and turns to face me and the hopeful whiteboard to my right. Here comes the fun part. I’ve been his student long enough to know what comes next. To take the next step in exploring the meaning of life and understanding the complexities of mitochondria, there first must be a journey into the past. Without pause, Havird transforms the atmosphere of our interview and brings it into the alternate dimension some like to call a lecture. “Let’s have a little history lesson about mitochondria.”
“What is the meaning of life?”
Havird’s sudden question prompts us both to laugh as if it is a menial joke and not a hot topic that humans have discussed since the very beginning of time. Out of all the organisms on Earth, we’re the only ones (that we know of) actively thinking about the meaning of life. Havird explains that in Lane’s book, the whole idea is that intelligence, consciousness, and other complex behaviors can only develop in a certain type of organism. We, as humans, happen to be a fine example of what those complex traits can accomplish.
As far as life outside of earth is concerned, Havird mentions the Fermi paradox and its correlation to Lane’s argument that we may not be able to see extraterrestrial organisms that resemble us due to the existence of a bottleneck–a great filter of some kind– that prevents the development of those complex traits. According to Lane, that filter could be the acquisition of mitochondria. When I asked Havird if he believed in aliens he asked me to reframe my question like he would if we were in class. “Well, do you believe in other life forms outside of earth?” He makes it clear that he believes there could be other organisms out there, but as far as whether or not they resemble us, he can’t be too sure.
In order to have a well-defined species, there must be reproductive isolation between populations. This isolation could be caused by many different factors, but evolutionary biologists have started to turn their focus on genetic reproductive isolation and how mitochondrial genes may be the star players in creating such reproductive incompatibilities.
Because mitochondria were once independent, free-living bacteria, they have their own genome. The handful of proteins within the mitochondrial genome play a large role in generating the energy within all our cells. Loss of function mutations in any of those proteins result in ATP not being made. In non-biological terms: that’s a very bad situation. With a few quick strokes, Havird draws out a cell with its mitochondrial and nuclear genome on full display. Proteins, created individually by both the mitochondrial and the nuclear genome interact to form protein complexes that make ATP. “We get this chimeric nature of energy production in the eukaryotes. It’s dependent on the coordinated action of these two genomes,” says Havird.
Havird continues to expound on his speciation lesson by drawing a new figure. This time, he shows me his all-green version of allopatric speciation. In this new figure, two geographically isolated populations respectively begin to accumulate mutations in both their nuclear and mitochondrial genomes. “As one genome starts to accumulate mutations, that should cause selection for complementary mutations in the other genome.” This pattern continues to produce matches between the two genomes over time. But what happens if the two populations meet? “If there is coevolution between the two genomes, this is going to lead to coevolved mitonuclear genotypes in each lineage of eukaryotes,” states Havird. And whenever those lineages start to interbreed you could uncover genetic incompatibilities involving mitochondrial genes.
Near the end of our conversation, Dr. Havird didn’t shy away from talking about his current research. At present, his lab is working on a system that was pioneered by Dr. Molly Schumer, a scientist and Assistant Professor at Stanford. Members of the Havird Lab are examining the physiological consequences of the incompatibilities that Dr. Schumer’s lab found in swordtail fishes (cue another whiteboard drawing by Havird) from Mexico who hybridize frequently in their native range. In order to see these physiological changes, the Havird Lab takes a look at mitochondrial function by examining the respiratory efficiency of the different complexes in the electron transport chain. Later, I was able to visit the actual laboratory and see the equipment used in this process–it looked like a smiley face.
The system that is perhaps most near and dear to Havird’s heart is all about shrimp! This system was actually the same one Havird studied for his Ph.D. program. Now he’s continuing his research with his own lab and a new purpose. The shrimp in question are only found in anchialine habitats in Hawaii. Havird suspects that they will be able to see selection to maintain mitonuclear compatibility in the shrimp populations. “We’re going to Hawaii in two weeks to sample this population for nuclear genomic data,” he says. I can tell that as much as he loves teaching, he’s eager to get back into the field.
“Mitochondria are important for everything,” says Havird. There’s no denying that these energy-producing organelles are important in maintaining cellular function throughout the human body; however, there is more and more evidence that shows the mitochondria in a new, and extraordinary evolutionary light.
Take it from Havird, mitochondria may have a thing or two to teach us about life itself.
It goes to show…they are so much more than the powerhouse of the cell.