The more you think about life on land, the less sense it makes. Life started in the ocean about 4 billion years ago, and for 3.5 billion years, it remained there. Evolution created organisms that had to stay wet- -they were essentially fluid-filled bags, and if they dried out, their circulatory systems would collapse, and most of their proteins and DNA would crumple up into uselessness. Without the ocean’s nutrient-filled currents, they would starve, and they and their fragile eggs and larvae would be immobile, unable to reach new or better habitats.
Seen from the sea, then, the land should equal death. Yet since animals, plants, and fungi first came ashore some 450 million years ago, life on land has been outrageously successful. True, land organisms have had to remain fluid-filled, DNA-based sacs, and they still rely on the old- fashioned, oceanic ways of getting food and energy, such as predation and photosynthesis. But according to the best estimates, there are now twice as many species on land as there are in the seas, and they produce some 50 times as much biomass. Furthermore, they manage this on only one-third the ocean’s breadth and in only a tiny fraction of its depth. And they achieved these luxuriant statistics in very little time. If ocean life were a 100- year-old man, life on land would be an 11-year-old child.
Researchers have tried to explain this land-sea paradox, in bits and pieces, without much success. But Mark and Dianna McMenamin, a husband- and-wife paleontological team, have an imaginative new hypothesis that they believe can explain it all, at one go. To understand the success of life on land, they say, you have to recognize that it is a unified whole. What makes it different from marine life is that unrelated terrestrial organisms--plants, fungi, and animals--form a vast number of direct, physical connections through which fluid can move. In effect, the McMenamins claim, life on land has not so much forsaken the sea as created a new sea within the sum of its tissue--something Dianna and Mark have dubbed Hypersea.
Hypersea is in many ways different from an ocean: for starters, it has no surface on which you can gaze, and it does not seek to be level. If you could look at life on land through a machine that registered only fluid, you would see great columns of nutrient-laced water rising--the columns would be where trees stand. You would see water flowing horizontally underground among plant roots and fungi, pouring into animals as they fed, moving as the creatures moved. According to the McMenamins, this liquid matrix has become Earth’s newest aquatic habitat, one that marine organisms have aggressively colonized. And in critical ways it behaves exactly like an ocean: the movement of fluid through Hypersea provides life with the same sustenance that ocean currents do. But there is one notable difference in the life it feeds: rather than being passive beneficiaries of an ocean that surrounds them, land organisms can control the currents within them. Thus, viewed as Hypersea, life on land couldn’t help being a smashing success.
The McMenamins propose Hypersea not as metaphor but as reality. If they are right, and Hypersea does actually ripple through all the plants on the surface of Earth, all the insects, the birds, the reptiles, the mammals, all the cells in all the bodies that crawl or walk upon the land, the implications are as vast as the sea itself. Hypersea not only offers, for example, an explanation for the largely mysterious emergence of life on land but it also suggests a number of bizarre life-forms that should once have existed and perhaps still do. It explains not only the land’s greater biomass and biodiversity but also such mysteries as why terrestrial food chains are so much shorter than marine ones. It could provide agricultural and medical researchers with new ways to understand pests and diseases. It could even reveal the future of evolution.
