I won’t go on about this cool new paper at length, for it’s already been described by Ed Yong at Not Exactly Rocket Science as well as in a piece at The New York Times. Still, it behooves us to know about it. The upshot is that a group of Russian scientists recovered from the Siberian permafrost a cache of seeds and fruits stashed by ancient squirrels, and managed to use tissue culture to regenerate plants from immature fruits. The estimated age of the seeds is 32,000-30,000 years old, so this is clearly the most ancient organism ever “revived.”
The plant, a species that still exists (at least the morphological similarities suggest conspecific status), is Silene stenophylla. Silene (of which there are several species) is also known as “catchfly” or “campion” (literate readers will recognize it as the flower with which Mellors the gamekeeper bedecked Lady Chatterly’s pubic hair in Lady Chatterly’s Lover). It’s often used in evolutionary studies because some species have separate sexes while others do not, and ditto for sex chromosomes. It could thus tell us something about the evolutionary origin of gender and gender-specific chromosomes. Some species are also gynodioecious (i.e. some plants are “female” [male parts sterile], while other plants are hemaphroditic), and this could also give us a clue to how “male” versus “female” plants arose.
But I digress. In a new paper published in the Proceedings of the National Academy of Sciencesby Svetlana Yashina et al., the authors describe finding a group of fossil burrows, 20-40 meters below the surface, in the permafrost of northeastern Siberia. Some of these burrows contained as many as 600,000 seeds/fruits! These were stashed by equally ancient ground squirrels of the species Urocitellus parryii:
Permafrost provides the dry and cold conditions needed to preserve seeds; that’s how they’re preserved in special seed banks. Attempts to germinate the seeds failed, but they managed to grow one species of Silene by dissecting out the “placental tissue” (special tissue in the fruit to which the seed is connected), culturing it in nutrient media and then adding hormones (auxins, etc.), to induce formation of roots and shoots. And they got the plant to grow, flower, and, after cross fertilization with other ancient plants, set seed. Here are two specimens of the plant grown from cultured ancient tissue:
The two articles cited above will give you more information. What interests me most about this is that the “species” still exists, and this allows us to see how much evolutionary change has transpired in 30,000 years. (This is similar to the way that bacterial evolutionists can freeze an ancestral culture and then, after reviving it, compare it to its descendants that have undergone many generations of evolution).
The plant appears to have actually changed during those 30,000-odd generations. (This is probably genetic rather than environmental change because the differences between ancient and modern plant are seen in the second generation of cultured ancient plants which have been produced by cross-mating them.) The authors note the differences:
Thirty-six ancient plants (12 from each fruit) and 29 extant plants were morphologically tested. All ancient plants were morphologically identical. During vegetative development, the ancient and extant plants were morphologically indistinguishable from one another. However, at the flowering stage they showed different corolla shape: petals of extant flowers were obviously wider and more dissected (Fig. 3). Moreover, all flowers of the extant plants were bisexual (b) (Fig. 3A), whereas the primary flowers (two to three in number) of each ancient plant were strictly female (f) (Fig. 3 B and C, f), and then bisexual flowers were formed on each ancient plant (Fig. 3C, b).
For those botany geeks among us, here’s Figure 3 showing the differences (click to enlarge):
The one thing I really wanted to know, and which the authors didn’t study, is whether the ancient plants are reproductively compatible with the modern ones. They crossed ancient plant with ancient plant, and showed that they cross readily, as of course do modern plants crossed with modern plants. But they didn’t cross ancient plants with modern ones! They need to do that.
If they found reproductive incompatibility in those crosses, that would suggest incipient (or full) speciation between ancestor and descendant, something that we rarely get to study because ancestor and descendants never get the chance to meet and mate (this would be like mating the 750,000 year old ancestors of Homo sapiens with modern H. sapiens, since a comparative number of generations have transpired). And even if reproductive isolation didn’t evolve, one can still study the genetic basis of differences in petal shape and appearance of different kinds of flowers. Ten to one the Russian team is doing this, and I look forward to the results.
h/t: Dr. John H. Willis III, esq.