Notes in June 2011: Cell Phone Warnings, Fossil Teeth

  • Cell Phone Warnings

    Recently, the World Health Organization's (WHO) International Agency for Research on Cancer (IARC) put the risks of cancer associated with cell phones in a 2B group: Possibly carcinogenic to humans, based on their analysis of available studies. From greatest to lowest risk the classifications are Group 1: Carcinogenic to humans, Group 2A: Probably carcinogenic; Group 2B Possibly carcinogenic; Group 3: not classifiable as to carcinogenicity; Group 4: Probably not carcinogenic.

    Scientists and journalists responded to this with their own interesting and sometimes quirky analyses. Many said the new information made them feel safe about cell phones and pointed out that the 2B group included the coffee. Others said they were concerned about the new classification, and focused on the fact that the 2B group includes DDT. And others argued in more complicated ways, things like - since DDT only affects eagles' eggs, they felt ok about cell phones. Some people reasoned that they know with certainty that tobacco is carcinogenic, and cell phones aren't in that category. How do people decide how to judge risk?

    Because logically, of course, some of this reasoning breaks down. It's not clear what people mean when they announce they'll take a risk with cell phones *because coffee is a possible carcinogen too*. Most likely they haven't read the research on the possible/maybe/sometimes connection between coffee and bladder cancer (the deciding factor for IARC on coffee). No, they're not thinking *bladder cancer*, they're thinking they'll take their chances with cellphones since they drink coffee all the time. But possible/maybe/sometimes isn't really reassurance.

    Some people say that since cell phones have been in use for 15 years or so, we would know if they caused cancer. But the use patterns were different, as were the strength of signal. And recall that cigarettes were only widely acknowledged to be carcinogenic in the 1950's and 1960's, when people had been smoking for hundreds of years. Then it took decades for that research to be acted upon. And people still smoke, no matter how clear it is that smoking causes cancer. At the present stage of cell phone research, we might not even know enough about physics and physiology to understand how cell phones cause or don't cause cancer. It adds up to a lot of unknowns.

    But still, everybody wants an answer. So do journalists and bloggers feel compelled to try to give one? This is sort of funny since no one really knows yet. But science journalists should understand how research works and the inherent uncertainty and risks and the unpredictability of evolving health research. So why feel compelled to provide an answer? Personally, (see, because we can't help ourselves) I think there's enough research that I won't walk around with my cell phone in my front pocket or stick a little mini cell phone inside my ear all day and night. And I hate to say this but I really do want to see more non-industry research. But that's based on what I know of the research, science, economics, and politics.

  • Our Ancestors' Social Groups...Two Million Years Ago

    Scientists looked at the teeth of two million year old fossils and found that female hominids were more likely to leave the area they were born in, whereas males were more likely to stay closer to the cave they were born to...Oh wait, that's not catchy. We should say something like this: "Ancient male hominids had 'foreign brides'", or, hominid men "like[d] their man caves", they were "mama's boys" or were "homebodies"? See, all the good ones are taken. But by all means, lead anachronistically to catch the reader's attention.

    "Foreign Brides"? Really? It's not cool enough that scientists figured out how to analyze the teeth of our human ancestors from 2 million years ago in order to determine their possible social group structure? 1

    Using newly evolved laser technology, Copland et al profiled the strontium mineral levels in the teeth from Australopithecus africanus and Paranthropus robustus, and from modern plant and animals around two caves in South Africa. Strontium moves up the food chain from plants to animals, and accumulates in developing teeth until about the age of eight. Scientists can analyze radioactive strontium levels in teeth for instance, and compare them to surroundings bedrock to determine birthplace. In this study, the two caves were within a band of dolomite bedrock in South Africa and non-dolomite geology surrounds this band. Researchers designated the dolomite band as local, and the non-dolomite regions further afield (~3 - 30km), as non-local.

    The teeth from both species were previously found to be similar in size, but importantly, females typically have smaller teeth than males. So the investigators found that females of the Australopithecine more likely had teeth with non-local strontium profiles, and the males teeth more likely to have a strontium profile reflecting their dolomite home turf. A probable explanation is that the females left the social structure they were born in to. This conclusion is supported by the pattern of female dispersal in our nearest ancestors, chimpanzees and bonobos. By comparison, in gorillas and other primates to whom we're not related, males tend to leave their natal group.

    1 Copland et al; Nature 474, 76-78 (02 June 2011) doi:10.1038/nature10149

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