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Once food had been plentiful, but no longer. In the early days of the colony, the amoebas had feasted on a rich supply of bacteria. But as the generations passed and the population swelled, they had hunted out their food supply. Now starvation threatens. Their home– a scrap of deer dung which once provided all their needs– has become a trap which they must escape if they are to survive. At last, one amoeba sends out a cry for help.

The starving amoeba begins to emit a chemical signal in the form of cyclic adenosine monophosphate, or cAMP. Nearby individuals sprout new pseudopods and crawl toward the source. They also begin to give off cAMP themselves, amplifying the call until the signal spreads to the far reaches of the colony. Amoebas cannot concurrently detect and produce cAMP, so they alternate, and the cells trace out intricate spiral patterns as they surge forward in waves.

The amoebas pile on top of one another in growing numbers until so many of them have joined the heap that this pile of microscopic single-celled organisms becomes visible to the naked eye. At first their behavior might seem odd; to gather together in the face of starvation surely ought to end in cannibalism or death. Not so, for they are capable of an extraordinary and rare transformation. The amoebas set aside their lives as individuals and join ranks to form a new multicellular entity. Not all the amoebas will survive this cooperative venture, however. Some will sacrifice themselves to help the rest find a new life elsewhere.

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