Chew more gum, for posterity

Behold, a discarded lump of chewed birch pitch from Denmark:

Awesome, I know. Heating up birch bark produces this dark, sticky substance that can be used as an adhesive, and also can be chewed like chewing gum. It apparently has some antiseptic properties. No one has told me yet what it tastes like, I guess I’ll have to try it for myself sometime.

That lump was thrown away 5700 years ago, after someone had been chewing on it for a while. What’s cool is that lots of DNA was extracted from it, and we know a bit about the person who’d been using it.

We successfully extracted and sequenced ancient DNA from a 5700-year-old piece of chewed birch pitch from southern Denmark. In addition to a complete ancient human genome (2.3×) and mitogenome (91×), we recovered plant and animal DNA, as well as microbial DNA from several oral taxa. Analysis of the human reads revealed that the individual whose genome we recovered was female and that she likely had dark skin, dark brown hair and blue eyes. This combination of physical traits has been previously noted in other European hunter-gatherers, suggesting that this phenotype was widespread in Mesolithic Europe and that the adaptive spread of light skin pigmentation in European populations only occurred later in prehistory. We also find that she had the alleles associated with lactase non-persistence, which fits with the notion that lactase persistence in adults only evolved fairly recently in Europe, after the introduction of dairy farming with the Neolithic revolution.

We also know that she had duck for dinner and had been snacking on hazelnuts. She carried the Epstein-Barr virus, so she’d probably had mononucleosis at some time in her life. She probably wasn’t a farmer, but was a member of a known hunter-gatherer population in central Europe, which fits with her diet of wild game and foraged nuts. Her descendants would eventually migrate north to colonize central Scandinavia, and intermingle with other hunter-gatherers migrating from the east.

Oddly, most of the popular press reports I’m seeing on this story call the gum-chewer a girl. I don’t know why, maybe it’s based on this reconstruction, but I don’t see any evidence in the paper to characterize her age — she could have been the Svyltholm Old Lady, for all we know.

I don’t chew gum, but maybe I should start, just to leave some trace of me to be found in 7000 AD. Now I just have to figure out where to leave my wads of gum to maximize their odds of being found…

Jensen, T.Z.T., Niemann, J., Iversen, K.H. et al. A 5700 year-old human genome and oral microbiome from chewed birch pitch. Nat Commun 10, 5520 (2019) doi:10.1038/s41467-019-13549-9


  1. says

    Sorry, PZ, but the gummianity of 7000 CE won’t be looking for human DNA, but clues to how ancient non-living material spawned living, intelligent gum beings like them.

  2. Jazzlet says

    The article I read said that for most of the birch bark gum that has been found in Europe with imprints of teeth those imprints are of juvenile teeth, so it appears that the adults were less likely to simply discard the gum, thus the probability is that the gum was used by a girl rather than a woman. The speculation is that when adults chewed birch bark gum they did so because they used it for something like gluing spear heads onto shafts.

  3. M'thew says

    Confirming Jazzlet’s input: From the Guardian:

    It is impossible to know her age, but given that children seemed to chew birch tar, the scientists suspect she was young.

    I’m just waiting for some of my regular internet haunts reporting on the conniptions that white supremacists, neo-nazis and others are having after learning that the ancestors of their beloved, Aryan-deemed Norsemen and Vikings were dark-skinned.

  4. Susan Montgomery says

    This calls for something unusual

    “The 30-year-old PhD student, studying electronic arts at Rensselaer Polytechnic Institute in Troy, New York, extracts DNA from each piece of evidence she collects, focusing on specific genomic regions from her samples. She then sequences these regions and enters this data into a computer program, which churns out a model of the face of the person who left the hair, fingernail, cigarette or gum behind.”

  5. stroppy says

    Chewing gum probably not a good idea if you have caps. I got an uncomfortable reminder of that a few years ago.

  6. wzrd1 says

    @2, they actually did recover her DNA from the gum, along with DNA of oral flora and fauna. Also, food residue was trapped in the gum, largely hazelnut and mallard duck.
    Rather sounds like a stuffing I made for a duck dinner.

    It would prove interesting if a full sequence could be found for Epstein-Barr virus, just to compare with the modern variants. Given the 50% of 5 year old children and 90% of the population having experienced EBV infection and a wide variety of potential links to an extremely wide assortment of human diseases, that could prove illuminating.

  7. barbaz says

    It is impossible to know her age, but given that children seemed to chew birch tar, the scientists suspect she was young.

    It’s impossible to tell if she was old, but she definitely was young at some point. And after 5700 years, who cares if you get her age wrong by 0.5%?

  8. PaulBC says

    Wasn’t this the subject of Vogon poety? “Ode to a lump of 5700 year old chewed gum I found under a rock in Denmark one midsummer morning.”

  9. lochaber says

    huh, that’s pretty cool.

    And about them being dark skinned, reminds me of a recent(?) genetic analysis of “Cheddar Man” in England, who was also dark skinned. 5700 years ago is a long time for an individual person, but an eyeblink in geologic time, and not even very long in human history. I wonder how quickly light skin genes spread throughout Europe and Asia.

    Duck and hazelnut doesn’t sound like a bad meal…

  10. PaulBC says

    I’m a little puzzled on the pigmentation finding. Assuming lighter skin is beneficial for producing vitamin D, then it seems really unlikely to have first emerged 5700 years ago. Humans have been living in northern latitudes for a lot longer than that. I wonder if vitamin D production is of only marginal benefit. It is definitely a liability if you don’t live in a high latitude with a lot of clouds (my genes are poorly adapted to where I live in California; my Irish skin is a quick death sentence without careful precautions).

    This person may also have come from a more recent migration. Now I’m curious. What is the oldest genetic evidence of light skin?

    Of course, it’s always good to undermine essentialist racial beliefs (sadly persistent despite overwhelming evidence).

  11. PaulBC says


    Chewing gum probably not a good idea if you have caps.

    5700 year old dental caps would have been a serious archeological find!

    (Missing your point I think.)