Tradeoffs. Should you wash your hands?

 Last time, I wrote about the somewhat controversial topic of “borrowing” your co-worker’s food. The choice to steal involves costs and benefits: the energy you gain from that food vs. the costs may you suffer from stealing. This is a general example of a tradeoff: You cannot be both good at stealing your co-worker’s food and in your co-worker’s good graces.

Tradeoffs come in all forms. For example, I often hear the following proverbial tradeoff for humans: “Jack of all trades, master of none.” If you’re okay at everything, you are not likely going to be great at any one thing. At its most basic level, this tradeoff involves investment. How much energy should you invest in one activity over another? Many tradeoffs involve investment. Though humans can reproduce as teenagers, many wait to reproduce until after they have stopped developing (e.g., mid-twenties). Such a choice, while for many occurs for social reasons, also exemplifies the tradeoff between investment in growth or reproduction (should I reproduce now and risk being unable to take care of my children because I’m not big and strong, or wait until I can take care of them but risk losing the opportunity to reproduce?). Information gathering can also be a tradeoff. Do you buy products spur of the moment, or carefully research? In this situation, you are trading off time and energy. If you research, you are using your time and mental energies when they could be used elsewhere. If you don’t research, you might pay too much, buy the wrong item, or be more likely to return the item later.

While these examples focus on people, all organisms face tradeoffs, many of which markedly resemble the ones above. Many non-human animals, for instance, feed on multiple items. The animal can thus choose between specializing on a particular food item or generalizing to eat everything. If the animal specializes, presumably it will become better at getting that item or getting more energy from that item. If the animal generalizes, it will have access to a greater variety of food, but may not get as much energy out of that food. This is analogous to the “Jack of all trades, master of none,” idea above in that you can be excellent at eating one thing, or good at eating everything, but not excellent at everything. Animals may also experience tradeoffs with responses to natural enemies, where “natural enemies” refers to predators and parasites. For example, hosts are exposed to many types of parasites throughout their lives, and hosts may invoke different defenses against those parasites. Hosts may therefore experience tradeoffs between different defense mechanisms (investing in behavioral defenses may mean less energy for immune defenses) or tradeoffs between the different types of parasites (being good against parasite A may preclude defense against B).

Such tradeoffs may make it appear that organisms are inappropriately adapted to their environments. “Why does that host suffer so much damage from that parasite?” However, such judgments need to account for the overall environment of the organism in question. Perhaps an organism is poorly adapted to a parasite because the parasite does not infect that many hosts in the population, and food shortage is far more important for survival to the host? If that is the case, the host may favor food acquisition at the cost of parasite defense capability. Additionally, if a host displays poor immunity, perhaps it exhibits numerous behavioral defenses? Such tradeoffs and environmental details, importantly, may make it appear that a host is acting maladaptively (i.e., in a manner that negatively impacts its survival and reproduction). To illustrate, have you ever touched a doorknob? And then ate something without washing your hands? Someone might be able to argue that this was “risky,” or even maladaptive, behavior because it exposed you unnecessarily to potential infectious agents. However, it’s a tradeoff. How much time and energy would you be wasting by washing your hands, or how much would you be damaging your hands by exposing them to basic chemicals, vs. the likelihood that you will get sick if you do not wash your hands? To really evaluate this scenario, we need to know more about the costs and benefits of washing your hands. Maybe in your culture, hand washing is considered unattractive, and so you are more likely to find a partner if you do not wash your hands, making hand washing maladaptive. Thus, the take home point: As is often the case in ecology, everything depends (on the details).



Hands are hard to draw.


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