It’s really no secret that despite being the most advanced creatures on the planet, humans are stuck with some horrible diseases and illnesses that can make us feel incredibly fragile.

We’re seemingly at the top of the food chain, but one nasty strain of bacteria or one displaced gene code and it’s game over pretty fast.
Why, though? Where did this susceptibility come from, and why are our genes mutating in ways that harm us?

The answer can be found about 50,000 years ago, when early humans were having fun with their Neanderthal neighbors.

Yes, it’s true: Neanderthals are the reason we have things like depression, celiac disease, and even cigarette addiction.

Since 2010, genetic archaeologists have been working to figure out these Neanderthal genes and why they’ve lasted this long and, in some cases, screwed us over.

Back then, some of these mutations were actually good! A gene variant found in Neanderthals allowed for better blood clotting. But now, too much clotting puts us at risk for stroke. Ironic, isn’t it?

Seriously though, there are some good variations that came about and still benefit groups today like breathing at high altitudes or fat tissue production.
By studying the way Neanderthal genes entered and mixed into our own gene pool, we can get a better understanding of where these mutations and diseases began.

We just aren’t totally sure why the more negative traits benefitted Homo sapiens in such a way that they stuck around.

Take, for example, HPV. When humans and Neanderthals interbred, their own strain mixed with our genes and resulted in cervical and mouth cancer.
However, we had our own strain of HPV to begin with. Why? Scientists are trying to figure that out.

Even more curious is the addiction to smoking. Considering smoking doesn’t appear in the record until about 5000BC, we’re pretty sure Neanderthals weren’t having a casual cigarette around the fire at night.

Instead, researchers argue it’s actually entirely possible the gene has more than one function and that’s why it’s stuck around so long. Remember, smoking addiction doesn’t inherently cause problems as long as you don’t ever smoke.

What about depression? For those of us who have it, it’s pretty difficult to imagine how or why something so debilitating could ever be seen as “beneficial.”

But 40,000-50,000 years ago is a long time. It’s almost impossible to imagine what the consequences of this variation could’ve been.

The blade of this discussion does have a double edge, though. Homo sapiens gave Neanderthals stomach ulcers, tapeworms and tuberculosis, and researchers believe this may have helped lead to the decline and eventual extinction of the prehistoric group.

Even still, there are areas of our DNA where no Neanderthals made their way in. Likely due to the effects being so disastrous they wiped out the population carrying them (and thus the gene), we see there has been selection for some traits over others.

But we also need to consider that 50,000 years is a pretty short amount of time considering the 6-million-year span of evolution, so it’s entirely possible traits are still being selected out of the genome.

Humans are strange beings, and their ancestors are even stranger. Even though we’ve mapped the genome, there’s still a lot to learn about ourselves and what makes us, us.

Will depression actually cease to exist someday? The answer is unclear, but next time you’re questioning why you can’t have a normal chemical balance in the brain, you’ll know who to blame.

Rachel is a senior Anthropology major, the President of the Anthropology Club, and is a staff writer for The Voice.