Neanderthal DNA may shape modern risks
The ancient ancestor suggested by this connection is the Neanderthal. People whose ancestors lived outside Africa often carry small stretches of Neanderthal DNA, inherited through interbreeding tens of thousands of years ago. Some of those stretches affect how the body responds to its surroundings—including, potentially, the immune system and traits related to mood.
That is a long way from saying a Neanderthal gene causes someone’s allergies or depression. These conditions arise from many interacting influences, and inherited variants can only shift risk, not dictate an outcome.
Why an old immune response can matter now
Neanderthals lived in environments with different microbes and other challenges. Genetic variants that helped their descendants respond quickly to infection could have been useful after modern humans entered new regions. But a highly reactive immune system can also mistake harmless substances—such as pollen—for threats. That overreaction is the basis of many allergies.
The same inherited DNA can have different effects depending on a person’s other genes, health, and environment. So Neanderthal ancestry is not a simple allergy switch; it is one small part of a much larger biological picture.
Mood is a more complicated link
Some research has associated Neanderthal-derived variants with mood-related traits, including depression. Such findings describe statistical links across groups, not a reliable way to explain an individual’s depressive episodes. They also do not establish that seasonal allergies and depression share one genetic cause.
The useful takeaway is less dramatic than “blame your Neanderthal ancestor”: ancient DNA still contributes to human variation, and a variant that once helped with one environmental challenge may have tradeoffs today. It can be part of a risk story, but it cannot tell you why one person feels ill in pollen season or experiences depression.
