Remembering the year (biologist style)
Olivia Judson adds a new post on different types of memory in honor of the end of the year.
Another year; another 584 million miles traveled on our endless journey ’round the sun; another set of joys and regrets, disasters and triumphs. And sitting here, reflecting on the year, I am also moved to reflect on the nature of memory — and on memory in nature. For the conscious, brain-based memories that we humans set so much store by are not the only memories out there.
She goes on to discuss memory in the immune system in animals and defensive memory in plants such as a wild tobacco.
We tend to think of memory as unique to animals. But it isn’t. Plants also have a form of memory. Yes: they, too, are shaped by what happens to them, and alter their responses to future events based on their experiences in the past.[…]Tobacco plants attacked for the first time take longer to mount their defense than tobacco plants that have previously experienced an attack. This isn’t because the previously attacked plants keep on producing a higher level of nicotine — they don’t. Nicotine is expensive for a plant to make (it takes a lot of energy and requires large amounts of nitrogen, which the plant might prefer to use for other purposes), so they only do it when necessary. No: the previously attacked plants respond to new leaf damage more quickly. And plants that have been attacked twice are faster to respond than plants that have only been damaged once. Somehow, they remember.
I saw Olivia Judson on a NOVA program today (on Tuesday the 29th) discussing evolution which got me thinking. Just as scientists compare and contrast, say, the genomes and embryos of different forms of life to learn their evolutionary heritage, I wonder if anyone has looked into whether plant and immune system (as well as any possible others) memory are evolutionary precursors to conscience memory. What, if any, are their relationships? I threw that question up in the comments section under her blog post so if anyone responds with anything interesting I’ll share it.