A Short History of Nearly Everything

London’s Natural History Museum is full of back corridors where scholars study samples—the museum contains over 15 miles of jars and folders containing everything from mollusk shells to pressed plants. Some scientists spend years studying one plant alone. Bryson enters the botany department and meets Len Ellis, who works as a curator of “bryophytes,” or mosses. There are 10,000 known moss varieties, though in the tropics more species are found each day. In fact, Ellis says that he has “no idea” how many species of moss live on Earth, though he thinks there are many more than the ones scientists have already discovered.

It takes about six months to catalog a new moss once it’s been discovered, and these species often disclose new mysteries. The London Natural History Museum has 780,000 moss samples so far, including 30,000 plant specimens from famous British botanist Sir Joseph Banks, who sailed to Australia with Captain Cook during the famed 1769 transit of Venus. In 18th-century Europe, plant collecting is a popular and lucrative recreational pastime, with new varietals earning handsome sums on the commercial market. To Bryson, the “volume of life on Earth” is “seemingly infinite.”

The sheer volume of species in the world (including plants and animals) demands a good classification system, or “taxonomy.” One such system is devised in the 1700s by eccentric Swedish botanist Carle Linné, who names weeds after people he doesn’t like. Linné dramatically simplifies existing species names, which are highly disorganized in his time. Linne is the first person to classify whales as mammals based on similarities in their respiratory systems. Today, nearly all of his names are still in use (with the exception of sexually vulgar ones, which he has a curious fondness for). Linné divides animals into six categories—mammal, reptile, bird, fish, insect, and worm—though it takes until 1902 for naming systems to be standardized on an international level. 

Taxonomy is fraught with duplications, however, because many species look very similar. Scientists also often disagree on how new species should be classified. The renaming of “chrysanthemum” flowers to “dendranthema” (for consistency purposes) in the 1980s is met with such uproar that the International Association for Plant Taxonomy has to change the plant’s name back to “chrysanthemum” in 1990. Frequent disputes and reclassifications mean that “we don’t have the faintest idea” as to how many species of life there actually are on Earth—estimates range from “3 million to 200 million.” Moreover, scientists think they’ve only discovered three percent of Earth’s species. There are also disagreements within sub-categories: for example, some scientists think that there are 4,000 species of earthworm, while others think that there are 12,000.

Estimates vary so much because it’s difficult to extrapolate from a sample to the world at large, and taxonomists often struggle to decipher 19th-century classifications when checking for duplications in historical publications. Bryson thinks we know “as little as we do” because of four reasons. First, most living things are very small. A typical mattress is home to 2 million microscopic mites, for example, though mites weren’t discovered until 1965. Bryson urges the reader to image how many equally small species exist in undiscovered parts of nature.

Second, scientists often don’t look in the right places. Historical searches focusing on Europe and North America, for example, overlook rainforests, in which over half of animal life and over two-thirds of plant life live. At least 99 percent of flowering rainforest plants have never been tested for their medicinal properties (since plants can’t flee predators, they often have inbuilt chemical defenses with profound medicinal potential). Third, there aren’t enough specialists. Fungi, for example, don’t entice many researchers, meaning that only 70,000 of a potential 1.8 million species have been cataloged so far.

Finally, the world is huge—air travel and communication are deceptive compared to how much literal ground there is to cover. The flightless “tahake” bird of New Zealand was pronounced extinct 200 years ago, but it was recently rediscovered alive and well in a remote rugged area of the island. Discovering all life would demand upturning every single rock on Earth. New species are also often discovered living in places assumed to be inhospitable to life (such as blind, colorless insects that live deep underground). It would demand an array of specialists waiting to analyze all these curious species, all willing to devote decades to one varietal alone, and there simply aren’t enough people interested in doing that.