eslie estimates that a medium-sized black pine can produce 10 billion pollen spores, mostly released over the course of a single week each year. The combination of abundance and durability has made pollen an important tool for understanding how plant communities change over long periods of time. The standard technique is to drill into a study site and extract a stratigraphic core, giving the researcher a sort of layer-cake look into the past. Archaeologists also sometimes scrape away the vertical surface of a dig to get a clean profile, then remove soil samples every few inches, working from the bottom to the top to avoid contamination by falling dirt.
Back in the laboratory, each sample goes through repeated hydrochloric acid baths, which destroy everything except the almost immortal exine. The palynologist then puts the material on a microscope slide to determine how many species are present (worldwide almost a half-million species make pollen) and calculate the proportion of different species. That makes it possible to describe how the world looked in different time periods.
A recent study in Science
, for instance, used pollen cores to demonstrate that extinction of Australia’s giant marsupials and other megafauna 40,000 years ago triggered the shift away from mixed rainforest habitat. Another study in Science
examined the pollen record for southern Greenland and found that a conifer forest grew there during a period of natural warming 400,000 years ago.
hat studying pollen gives scientists, in other words, is the means to do what the poet William Blake once imagined:
To see a world in a grain of sand,
And a heaven in a wild flower,
Hold infinity in the palm of your hand,
And eternity in an hour.
Add to that the ability to solve the occasional murder and palynology begins to sound like the kind of career a kid could grow up dreaming about.