On a recent journey into Puerto Rico’s stunning El Yunque rainforest, the thought kept hitting me: Life misses no opportunity. Every surface was blanketed in green, leaves and stems optimally shaped to channel the lavish rainfall and compete for sunlight. Sierra palms perched on their roots above the waterlogged ground; blooming bromeliads nestled in the branches of lofty tabonuco trees. It called to mind Charles Darwin’s famous image of the entangled bank, “these elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner, [all] produced by laws acting around us.”
With those words in mind, the articles in this issue take on new shadings. Life’s persistence connects us across time, to the early ancestors of mammals that lurked among the cycad trees of Mongolia some 300 million years ago (see page 44). The notion also contains contemporary lessons of life-and-death practicality. Tumor cells within a patient’s body make their own inevitable efforts at surviving, multiplying, and colonizing new territory. In the process, those cells can rapidly find ways around medicines intended to shut them down. Such understanding is essential to defeating cancer—even if we can get the right drugs to the right patient (page 56).
In the loftiest sense, the entangled bank of life may even span outer space. Just as every remotely hospitable environment on Earth teems with living things, so may the buried lakes and ocean of Jupiter’s moon Europa (page 30). Finding evidence of biological activity there (or on Mars, Titan, or Enceladus) would be momentous. If life could arise in two different places in our solar system, it could presumably do so a million times, or a billion, on planets throughout our galaxy—because, again, life misses no opportunity. A single alien microbe would suggest that life is encoded into the very laws of the universe. Imagine: a living cosmos. To quote Darwin again, “There is grandeur in this view…from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.”