What could cows and cockroaches possibly have in common? Cows are large animals which provide man with milk and meat and hides, while roaches are squalid insects which do not provide man with anything, except perhaps to serve as objects of his hatred.
But different as they are, cockroaches and cows do share one important characteristic: They both owe a large measure of their success in life to friendly bacteria which spend their lives inside their host’s bodies. It is thanks to their unseen germ partners that cockroaches are able to eat almost anything they can find in our kitchens, and cows can eat grass.
In cows, the bacteria live in the first two of four stomachs. Here the bacteria go to work, breaking down the tough cell walls of the grass. The cow’s digestive juices can’t dissolve this material, called cellulose, but the bacteria thrive on it. They turn it first into sugar, of which they eat a portion themselves, and turn the remainder into various nutritive organic acids, which become the chief source of energy for the cow.
When you see a cow chewing her cud, she is grinding up some of the undigested grass from her first stomach, in order to help the bacteria get at the cellulose. When the bacteria colonies derive a rich diet from their labors in the cow’s fore-stomachs, they multiply very rapidly. But this doesn’t concern the cow, because the excess population is simply swept into the final stomachs, where they are killed by the digestive juices. In fact, their bodies become a source of vitamins, fats and protein which the cow needs!
Science has not learned nearly as much about the mutually beneficial relationship between cockroaches and their bacteria partners, but it is known that each is totally dependent upon the other. The bacteria species apparently cannot live outside their hosts, and roaches reared without the usual resident bacteria are stunted, weak and abnormal.
How roaches control their bacterial populations, and exactly how the bacteria aid in the digestive process are still mysteries, but it is known that they are an enormous help to the host roach in converting food to energy. The bacteria normally live only in specialized cells found in organs called “fat bodies,” which chiefly serve the insects as fat storage vaults. However, when female roaches approach maturity, the bacteria increase in number and many move to the ovaries. Here they beneficially infect the eggs shortly before they are laid, so that each new roach will get a proper start in life.
Cows and cockroaches and bacteria: What a strange mixture! We usually think of bacteria as harmful but, as we have seen, it is not always so. They also work cooperatively with the other grass-eaters, such as horses, sheep goats and rabbits, and even with wood-eating termites.
How did this unlikely pairing and sharing get started? Did a group of patriarch microbes decide they’d dwell peaceably with grass-eating animals, in return for snug quarters and plenty of food brought to the table? Or did ancient animals make the first overtures?
Neither can be the case. Such mutual dependencies cannot develop, simply because they could not have gotten started. Grass-eaters can’t eat grass without help, so there were no grass-eaters before the dual relationship was fully functioning. Similarly, the grass-digesting bacteria cannot survive and thrive without protection.
Each partner needs the other, and has from the beginning. This is marvelous in our eyes, because it is a manifestation of the work of God. Only He could bring together the candidates for partnership. Only He could create the whole panorama of abundant life, with every species of plant and animal designed to function in its own sphere and environment.
And this is precisely what the Bible speaks of in Psalm 104, when it says: “He causes the grass to grow for the livestock, and plants for man to cultivate, that he may bring forth food out of the earth…” (verse 14), and again: “Yahweh’s [that is, God’s] trees are well watered, the cedars of Lebanon, which he has planted…” (verse 16). And yet again: “These all wait for you, that you may give them their food in due season. You give to them; they gather. You open your hand; they are satisfied with good. You hide your face: they are troubled; you take away their breath: they die, and return to the dust. You send forth your Spirit: they are created. You renew the face of the ground.” (verses 27-30)
When we think of these things, we must conclude with the psalmist: “Let your meditation be sweet to him [God]. I will rejoice in Yahweh [that is God] (verse 34).
(All Scripture is quoted from the World English Bible translation.)