Several Short Sentences About… Seeds

image by Virvoreanu-Laurentiu on pixabay, CC0

I‘ve been reading Washington biologist Thor Hanson’s fascinating book The Triumph of Seeds. The book contains so many amazing facts about these little-studied (except for agricultural propagation purposes) evolutionary innovations, that they’ve prompted me to create a fourth post in my “several short sentences…” series about unique species of life (previously: sharks, bats, jellyfish). So here we go: Several short (and not-so-short) sentences about seeds:

1. Seed structures are so diverse that it’s sometimes hard to say exactly what a seed is, and where it ends and other parts of the plant begin. But a leading biologist, Carol Baskin, uses this handy definition: “a seed is a baby plant, in a box, with its lunch”. The size and durability of the ‘box’, and of the ‘lunch’ have evolved to match the threats of the seed being prematurely eaten or destroyed, and the amount of time the seed normally needs to survive before it finds a suitable place to germinate. Hence coconuts (ocean journeys before germination), avocado pits (waiting for enough nearby water), dandelions (“over there will do”), and conifers (“right here is fine”).
2. The myth that spore-reproducing plants dominated until the end of the hot, wet Carboniferous is untrue. Seeds co-evolved with spores, and have more recently prevailed because their means of reproducing is simpler and more reliable. The Carboniferous myth remains because the hot wetlands during that time, where spore-bearing plants thrived, were perfect for fossil production, while the more temperate higher-altitude areas, where seeds prevailed, did not tend to produce fossils.
3. The first stage of most seeds’ growth involves simply bloating up the cells with water, often to hundreds of times the seed’s original size. During that time, they use a variety of alkaloid chemicals, almost all of which are now employed by humans, to inhibit cell division. Those chemicals, which also serve to ward off pests, include caffeine, capsaicin, pepper, many modern drugs, and some of the planet’s most toxic poisons (eg ricin, henbane, cyanide, warfarin), which have been used not only as human and pest poisons but also, in smaller concentrations, for their cell-destroying properties in treating cancers and other diseases. Only when the then water-filled cells have shot out far enough from the seed to resist the toxins, does growth by cell division (requiring use of the ‘lunch’, with its evolved customized mix of starches, oils, fats, waxes, proteins and other energy sources) begin.
4. We can only guess how seeds ‘know’ when to start germinating. It is known that they can detect the qualities of surrounding soils, and the angle and amount of available sun even through feet of snow. It may well be that their means of ‘navigating’ their new environment are as sophisticated as that of birds (which we also know almost nothing about).
5. More than 70% of human farmlands are planted with grains, all of them cultivated through selective breeding from primeval grasses for the simple reason that grasses are the lowest-maintenance plants on the planet, due to the ease with which their seeds proliferate, and they contain starches which the human body can easily convert to energy. More than half of all human calories consumed come from grains.
6. Human digestive systems have co-evolved with the (mostly plant-based) foods we eat. We could no longer, for example, survive on the diet that our nearest neighbours the chimps thrive on, because our bodies can no longer break down many of the foods they eat; as early as 800,000 years ago we became, and are now of necessity, the “cooking primate”. Likewise, we could not survive now on a raw meat diet, because our modern bodies would consume as many calories trying to chew and digest the meat as it provides to us.
7. Seed banks and agriculturalists are now planning on ways to gradually replace the world’s largest crop — wheat — with more heat- and drought-resistant sorghum, starting in areas closest to the equator, as the earth’s temperature heats up to the point wheat will no longer grow. Seed banks are so important because food plant biodiversity is now so impoverished that the remaining species are hugely vulnerable to new plant pests and climate change, so alternatives need to be kept on the ready, and are regularly being introduced. Seed banks work in tandem with the many seed-saver exchanges around the world.
8. So much of the world depends heavily on imported seed grains that Lewiston, Idaho has become the world’s third largest ‘seaport’ for grain traffic (90% of it bound for Asia). This required the construction of a massive series of dams on the Snake and Columbia rivers to ‘quieten’ these rivers enough to barge the grain to Portland, Oregon. The hydroelectric energy produced by the dams was only a side-benefit and afterthought of the dams’ construction.
9. Everywhere grain is grown, it is rotated with beans and other legume crops. Not only does the rotation enrich the soil and allow more and richer harvests, eating grains and beans together provide much greater nutrition than eating either alone. Beans are still the main source of protein in much of the world.
10. Just as selective breeding of grains and animals has produced much higher-yielding human foods, the same patient breeding has produced most of the vegetables we think of as ‘natural’ crops (while drastically reducing their diversity). For example, a single nondescript coastal mustard plant has been selectively bred to produce all moderns strains of cabbages, collard greens, kale (by selecting for fuller leaves), Brussels sprouts, cauliflower, broccoli (by selecting for larger buds and shoots), and kohlrabi (by selecting for flat, edible stems). These vegetable ‘staples’ are all, essentially, human ‘inventions’.
11. Hand pollination of dates and figs (which for most of human existence have been the largest component of our diets) dates back over 4,000 years. Date palm seeds from ancient seed banks have been found to still germinate 2,000 years after they were collected.
12. Guar gum, a thickener made from a seed that grows almost entirely in India’s deserts, is so essential to modern industry that it now constitutes 30% of the cost of fracking operations, and its scarcity and resultant high price has forced food companies to replace its use with locust bean gum and fenugreek to keep products affordable.
13. Bird beak and rodent jaw shapes can evolve significantly in as little as a single generation to adapt to changes in the prevalence and characteristics of local seeds and nuts. The seeds and nuts then evolve to respond to the birds’ and rodents’ advantage, in a never-ending ‘arms race’. Since transport by birds and rodents is essential to many seeds’ successful reproduction, they can’t be so hard to crack that the predators give up dispersing them, or so easy to crack that they’re eaten on the spot. It’s a delicate balance.
14. Our skull shape and tooth organization and structure evolved to enable us to safely bite through nut and other seed shells (“the premolars, right behind the canines”). We instinctively ‘know’ exactly how to do this.
15. Columbus’ voyages were considered largely a failure by his sponsors, since their objective wasn’t to ‘discover’ new lands but to find and bring back nutmeg, pepper, and other rare and popular spices. But what he did bring back, ají, aka chiles, unknown outside the New World, eventually became the most popular spice in the world, and are now grown everywhere. Chiles are only ‘hot’ in the sense they fool our taste buds, and are only so in wet locations where their ‘hotness’ is essential to keep fungi at bay. Birds’ taste buds don’t respond to this trick, so they can eat ‘hot’ spicy seeds with impunity. Chiles were actually used as an antifungal, preservative, and rodent repellant, before they were used as food flavouring.
16. Most primates use seeds and other plant extracts for medicinal purposes, including pain relief, anti-inflammatory and wound and infection healing.
17. Coffee may be the principal determinant of the era of social change known as the Enlightenment. Coffee replaced beer as the beverage of choice at that time (before that, the average adult consumed three times as much beer as we do now), and institutions such as Lloyd’s insurance, the Bank of NY, the London Stock Exchange, Christies’ and Sotheby’s auction houses, and the Royal Society all began as informal meetings in public coffee houses. Coffee was unknown in the New World until it was transplanted there in the mid-1700s. Many plants (such as citrus fruits) carry caffeine in their flowers, because it’s as addictive to bees as it is to humans.
18. The castor bean, known for the production of castor oil, also is the source of ricin poison, and of Castrol motor oil, because the bean oil’s lubricating qualities are essential to high-performance racing car engines, and no petroleum-based lubricants measure up.
19. Cotton is another plant which was unknown in the New World until a few centuries ago, but its journey didn’t happen as a result of transport by human explorers or birds. Cotton seeds actually floated across the Atlantic Ocean and germinated in the New World, two different strains in two different places, where it was then ‘discovered’ by Atlantic coastal tribes. It’s evolved to be the main source of fabric everywhere on the planet.
20. There is no ‘direction’ to the evolution of seeds and other means of plant procreation. Both seeds and spores have evolved over hundreds of millions of years, but they are both relative newcomers to the propagation of life on earth. Sharks have been around much longer than trees. And some of the most ancient seed and spore mechanisms continue to be used by plants alongside very recent innovations. And they were both cosmic accidents, not necessarily the only ways for plant life to propagate. For example, orchids technically have seeds, but their seeds are tinier than dust particles, have no ‘box’ (seed coat or case) and no ‘lunch’ (initial nutrition provided by the parent plant), and they can take eight years to germinate. The tiny seeds form symbiotic relationships with mycorrhizal fungi, with each providing essential nutrients to the other. Had the climate been very different when seeds first evolved, the orchids’ means of propagation might have prevailed, meaning all the seeds, nuts and fruits upon which so much life (and civilization) depends might never have emerged, and what we call ‘life’ would have looked, today, unimaginably different.