>  Not sure what you mean by "completely genetic".  What cause other than
>  genetic would "handedness" be due to?

Certain left and right handed planktonic forams correspond very well to water temperature and thus provide a good marker, e.g., for glacial versus interglacial intervals in the geologic record.  (Mollusks also provide good indicators, but in different contexts-it's easier to spot Arctica islandica than forams in an outcrop, but harder to get a good specimen of Arctica out of oil well cuttings.)  This has been thought of as a temperature-controlled intraspecific variation, but recently has been suggested to be different, albeit similar, species with different temperature preferences.

    Dr. David Campbell
    Old Seashells
    University of Alabama
    Biodiversity & Systematics
    Dept. Biological Sciences
    Box 870345
    Tuscaloosa, AL  35487-0345 USA
    [log in to unmask]

That is Uncle Joe, taken in the masonic regalia of a Grand Exalted Periwinkle of the Mystic Order of Whelks-P.G. Wodehouse, Romance at Droitgate Spa

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