john hawks weblog

paleoanthropology, genetics and evolution

pathology

  • Tracing teeth troubles with fossil bacteria

    Sun, 2013-02-17 19:36 -- John Hawks

    Ed Yong has a great account today of some research from Alan Cooper's lab on the oral microbiome in pre-agricultural and post-agricultural Europeans: "Prehistoric Plaque and the Gentrification of Europe’s Mouth".

    The hunter-gatherers had a diverse array of bacteria including several groups that are associated with good health. That fits with the relative absence of tooth decay or gum disease among modern or prehistoric hunter-gatherers. “They were at the end of a long period of happy co-evolution between us and oral bacteria,” says Cooper.

    The advent of farming disrupted that tango. After the Agricultural Revolution, as humans began to chow down upon barley, wheat and other domesticated crops, the diversity of the mouth microbes fell, and species associated with oral diseases became more common. “Eating all this soft squishy carbohydrate and leaving it lying around the base of your teeth is effectively inviting in a whole new range of bugs to take up permanent residence in your mouth,” says Cooper.

    I'll have some more comments on this new research when I can sit down to write them up. I've been waiting for this to come out for quite a long time -- I first heard about the research almost three years ago. The potential to characterize oral ecology across time is immense, and we have some excellent data on dental pathologies across the entire timespan. Caries and other dental pathologies are very new in human populations, and although starchy diets have been blamed, very little has been known about how oral bacteria themselves may have become more pathogenic over time. This study is really great because it opens a new door to looking at this evolution across time. We will need to compare this record with the evidence for morphological change in teeth across the same time span. Smaller teeth may have been a consequence of selection associated with dental pathology in agricultural peoples.

    Next we will need to compare across space -- including greater sampling of oral microbiome variation among living humans. This is another new area in which we know more about prehistoric people than we do about living human variation!

    Tags: 
    microbiome
    teeth
    pathology
    health
    Neolithic
    recent selection

  • Quote: Washburn on early theories of human evolution

    Sun, 2011-01-16 15:49 -- John Hawks

    Sherwood Washburn, in a lecture published in 1982 [1]

    The early theories of human evolution are really very odd, if one stops to look at them. David Pilbeam has described the early theories as "fossil-free." That is, here were theories about human evolution that one would think would require some fossil evidence, but in fact there were either so few fossils that they exerted no influence on the theory, or there were no fossils at all. So between man's supposed closest relatives and the early human fossils, there was only the imagination of nineteenth-century scientists. For example, the scientists could not decide whether the original Neanderthal skeleton was a genuine fossil or a pathological specimen. Major scientists were on both sides of this debate, and it was not until a number of skeletons were found many years later that it was pretty well accepted that the Neanderthals formed a race of humans that lived in Europe before modern humans occupied that area. Even so, the Neanderthals were described as "uncouth, repellent, unattractive, incapable of fine coordination of the fingers, and certainly belonging to a different species." This is science derived directly from bones -- "uncouth, repellent, and unattractive"? Who felt this way about the skeletons?

    References

    1. Washburn S. Fifty years of studies on human evolution. Bulletin of the American Academy of Arts and Sciences. 1982;35:25–39.
    Tags: 
    pathology
    history of anthropology
    Neandertals
    Sherwood Washburn

  • Bone is super-interesting, but not an energy sink

    Wed, 2009-04-29 08:57 -- John Hawks

    Natalie Angier's article, "Bone, a masterpiece of elastic strength," is pretty cool. It describes the case of Harry Eastlack, a sufferer from fibrodysplasia ossificans progressiva, a kind of ossification of the soft tissues. I've seen his skeleton at the Mutter Museum, it's incredible the extent to which bone invaded the rest of his body. It's a great opportunity for her to talk about the constant reconstruction process of the skeleton:

    Bone also has a crack repair team, in every sense of the word: osteoclast cells that dig around the cracks, using acids to wipe away the old matrix, and osteoblast cells that migrate in and secrete fresh spacklings of bone. “Bone remodeling is going on simultaneously in hundreds of locations a day,” Dr. Karsenty said. It’s our private MASH, he said, our ambulatory surgical unit that helps keep us on our feet.

    I had to comment though, because of this:

    But like all forms of health care, bone repair doesn’t come cheap, and maintaining skeletal integrity consumes maybe 40 percent of our average caloric budget.

    Not a chance. Now, the stuff about hormonal communciation between bone and gut is true, and is a very current line of research. But 40 percent of BMR? I haven't found yet a reference that lists the mass-specific energy consumption of bone tissue -- it's such a small component of the body's energy budget that nobody bothers. Rolfe and Brown (1997) review energy metabolism of different tissues, listing liver, GI tract, kidney, lung, heart, brain, and skeletal muscle which sum up to 88 percent of oxygen use in humans. That leaves 12 percent for everything else, including two high-mass tissues, bone and skin. Heck the paper lists extra bone as one reason why bigger animals have lower mass-specific energy requirements!

    So no, bone is not drawing 40 percent of your caloric budget. However, your brain is drawing 20 percent.

    References:

    Rolfe DFS, Brown GC. 1997. Cellular energy utilization and molecular origin of standard metabolic rate in mammals. Physiol Rev 77:731-758. Abstract

    Tags: 
    disease
    bone
    pathology
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Neandertals

For years, I've worked on their bones. Now I'm working on their genes. Read more about the science studying these ancient people.

Denisova

From a finger bone of an ancient human came the record of a completely unexpected population. My lab is working on the science of the Denisova genome.

Acceleration

The advent of agriculture caused natural selection to speed up greatly in humans. We're uncovering some of the ways that populations have rapidly changed during the last 10,000 years.

Malapa

Just outside Johannesburg, the Malapa site is producing some of the most exciting finds in human evolution. This site is the headquarters of the Malapa Soft Tissue Project.