Attempting to selfishly gain an immediate advantage in a situation where others are co-operating is called social cheating. Many people are likely to bitterly recall an experience of this, queue jumping is a classic example, and a wide variety of other organisms undergo the same injustices. Cheaters in theory should have an evolutionary edge, but social co-operation remains at the base of almost all populations. This is a mystery that scientists have been intrigued by for years, as there is very little we really understand about these behaviours and how they co-exist.
Social systems can be ‘modelled’ in much simpler organisms than us; the social amoeba for example. Dictyostelium discoideum (Dicty), are generally alone throughout their lives, but for one 10 hour period. This time is where they become social in order to release spores that will grow into new amoebae. To do this they form ‘fruiting bodies’, where some Dicty give up their lives and harshly but more importantly; their bodies. These form a stalk, the top of which the spores can be released from. However some Dicty cheat - there are amoebae that climb straight to the top to release their spores and contribute less to the stalk. By doing this they release more spores than other, co-operating amoebae and so gain an evolutionary edge, passing on more of their genes. But this advantage cannot be significant, as otherwise they would overrun the co-operators and drive them to extinction.
Social systems can be ‘modelled’ in much simpler organisms than us; the social amoeba for example. Dictyostelium discoideum (Dicty), are generally alone throughout their lives, but for one 10 hour period. This time is where they become social in order to release spores that will grow into new amoebae. To do this they form ‘fruiting bodies’, where some Dicty give up their lives and harshly but more importantly; their bodies. These form a stalk, the top of which the spores can be released from. However some Dicty cheat - there are amoebae that climb straight to the top to release their spores and contribute less to the stalk. By doing this they release more spores than other, co-operating amoebae and so gain an evolutionary edge, passing on more of their genes. But this advantage cannot be significant, as otherwise they would overrun the co-operators and drive them to extinction.
 |
| The Dicty amoebae begin as single celled organisms, before congregating as a multicellular ‘slug’, which then gives rise to fruiting bodies with spores atop long stalks. In the species shown here, each of the sporangia was 2-3mm tall. Image credit: © Lairich Rig, via geograph (CC BY-SA 2.0) |
