God and Nature 2025 #4
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By Andrew D. Sweet
I recently read a story about a trap-door spider from Australia that lived to be over 40 years old (1). We know she lived so long because scientists studied her for nearly as many years. These spiders live fascinating lives, meticulously arranging small sticks around the entrances to their underground burrows as an “alarm system” to alert them of approaching prey or enemies. And so lived this particular spider, for over 40 years in the same burrow near an acacia tree. What an amazing creature! It’s these kinds of examples from nature that cause us to joyfully sing out Psalm 19. The Heavens indeed declare!
However, this story ends with a gruesome twist. Scientists went to check on the old spider one day and found her burrow unguarded and in shambles. The sticks that were usually neatly arranged had been scattered and the spider was nowhere to be seen. The likely perpetrator: a parasitic wasp. These wasps (“parasitoid wasps”) lay their eggs in other living arthropods by piercing the exoskeletons of their hosts with needle-like structures at the end of their abdomens. The wasp eggs continue developing inside the host and eventually hatch as hungry larvae. To survive, the larvae eat their host alive, eventually eating their way out to continue their life cycle and leaving their doomed, partially consumed host behind to die. In the case of our 40-year-old spider, a wasp likely got through the covering to the spider’s home and laid eggs in her body, condemning the spider to eventually be killed by the wasp’s voracious offspring.
I recently read a story about a trap-door spider from Australia that lived to be over 40 years old (1). We know she lived so long because scientists studied her for nearly as many years. These spiders live fascinating lives, meticulously arranging small sticks around the entrances to their underground burrows as an “alarm system” to alert them of approaching prey or enemies. And so lived this particular spider, for over 40 years in the same burrow near an acacia tree. What an amazing creature! It’s these kinds of examples from nature that cause us to joyfully sing out Psalm 19. The Heavens indeed declare!
However, this story ends with a gruesome twist. Scientists went to check on the old spider one day and found her burrow unguarded and in shambles. The sticks that were usually neatly arranged had been scattered and the spider was nowhere to be seen. The likely perpetrator: a parasitic wasp. These wasps (“parasitoid wasps”) lay their eggs in other living arthropods by piercing the exoskeletons of their hosts with needle-like structures at the end of their abdomens. The wasp eggs continue developing inside the host and eventually hatch as hungry larvae. To survive, the larvae eat their host alive, eventually eating their way out to continue their life cycle and leaving their doomed, partially consumed host behind to die. In the case of our 40-year-old spider, a wasp likely got through the covering to the spider’s home and laid eggs in her body, condemning the spider to eventually be killed by the wasp’s voracious offspring.
parasites are...necessary participants in the life-giving systems that sustain all biota. |
The macabre conclusion to this story elicits a very different response, one that likely doesn’t involve declaring God’s handiwork. Fifteen years ago, I would have seen the moral of this story as having something to do with the Fall, creation groaning, etc. Parasites clearly have no place in God’s Edenic plans for the earth, right? Well, now I study parasites for a living. My vocation has certainly challenged my understanding of how parasites fit into God’s good creation. Certainly, our failures have a negative effect on the natural world around us, even if that is manifested in our shortcomings as stewards. Yet, I do think parasites, in all their horrific and stomach-churning existence, declare God’s glory and reflect His character. I want to share three facets about parasites that have shaped my view, and which will hopefully challenge your perceptions of these creatures.
First, we are now beginning to understand how important parasites are in food webs, those intricate connections between different organisms that underpin all of life. In the past, scientists studying food webs did not include parasites in their models, but that has been changing. More recently, several studies incorporating parasites in these webs have demonstrated a crucial reality: parasites are ubiquitous (parasites likely make up more than 50% of species on earth) and firmly engrained in all levels of food webs. It turns out, parasites are not life-stealing freeloaders holding back their hosts from reaching their (our?) full potential, but rather necessary participants in the life-giving systems that sustain all biota. Remove parasites, and life as we know it could unravel.
Second, although many parasites cause sickness and pain themselves, they also protect their hosts from even worse parasites and diseases. Parasites are often adapted to live in a particular slice of their environment, where they play important roles in helping to maintain those ecosystems (moving resources, mediating interactions between different organisms, etc.). Without the parasites, their ecosystems do not function well, and the organisms living in those environments are worse off. For example, there is evidence that the presence of intestinal worms helps prevent autoimmune diseases in humans (part of the “Old Friends Hypothesis”). To summarize, and echoing the conclusions of a well-cited paper, healthy ecosystems are rich in parasite species (2).
Finally, parasites provide us with amazing examples of adaptation. I’ve alluded to this point in my previous two examples, but I think we should explore it more. Let’s consider the parasites I study: bird lice. These little insects have special features to live on feathers, where they survive by eating feathers and skin (and sometimes blood). Some lice have evolved particular shapes that allow them to live on specific parts of a bird (wing, body, or head), which keeps the lice safe from being removed by their hosts. Some lice have also evolved coloration that allow them to blend in with their host’s feathers (3). In part because of these adaptations, bird lice tend to be very host-specific, meaning a single type of louse will only be found on a particular group of birds. All of this biodiversity and specialization existing within the feathers of birds that visit our backyard feeders!
With these three examples in mind, let’s (re)consider parasites. Do they cause physical hardship, pain, and death? Absolutely. And we are most certainly called to help relieve the suffering that parasites cause. But, paradoxically, these creatures—sucking, chewing, gnawing, burrowing creatures—also help to sustain life, protect against disease, and are inseparably woven into the fabric of earth’s ecosystems. How humbling and gracious that our lives are in some ways propped up by what we often dismiss as vile; organisms that, if we peer past our visceral reactions, can be as fascinating as the most distant galaxies. I, for one, embrace this paradox and can confidently say that parasites do indeed reflect God’s goodness and display His handiwork.
References
Andrew Sweet is an Associate Professor of Evolutionary Biology at Arkansas State University. His research focuses on the evolution of birds, parasites, and genomes. He teaches courses in evolution, genetics, and zoology.
First, we are now beginning to understand how important parasites are in food webs, those intricate connections between different organisms that underpin all of life. In the past, scientists studying food webs did not include parasites in their models, but that has been changing. More recently, several studies incorporating parasites in these webs have demonstrated a crucial reality: parasites are ubiquitous (parasites likely make up more than 50% of species on earth) and firmly engrained in all levels of food webs. It turns out, parasites are not life-stealing freeloaders holding back their hosts from reaching their (our?) full potential, but rather necessary participants in the life-giving systems that sustain all biota. Remove parasites, and life as we know it could unravel.
Second, although many parasites cause sickness and pain themselves, they also protect their hosts from even worse parasites and diseases. Parasites are often adapted to live in a particular slice of their environment, where they play important roles in helping to maintain those ecosystems (moving resources, mediating interactions between different organisms, etc.). Without the parasites, their ecosystems do not function well, and the organisms living in those environments are worse off. For example, there is evidence that the presence of intestinal worms helps prevent autoimmune diseases in humans (part of the “Old Friends Hypothesis”). To summarize, and echoing the conclusions of a well-cited paper, healthy ecosystems are rich in parasite species (2).
Finally, parasites provide us with amazing examples of adaptation. I’ve alluded to this point in my previous two examples, but I think we should explore it more. Let’s consider the parasites I study: bird lice. These little insects have special features to live on feathers, where they survive by eating feathers and skin (and sometimes blood). Some lice have evolved particular shapes that allow them to live on specific parts of a bird (wing, body, or head), which keeps the lice safe from being removed by their hosts. Some lice have also evolved coloration that allow them to blend in with their host’s feathers (3). In part because of these adaptations, bird lice tend to be very host-specific, meaning a single type of louse will only be found on a particular group of birds. All of this biodiversity and specialization existing within the feathers of birds that visit our backyard feeders!
With these three examples in mind, let’s (re)consider parasites. Do they cause physical hardship, pain, and death? Absolutely. And we are most certainly called to help relieve the suffering that parasites cause. But, paradoxically, these creatures—sucking, chewing, gnawing, burrowing creatures—also help to sustain life, protect against disease, and are inseparably woven into the fabric of earth’s ecosystems. How humbling and gracious that our lives are in some ways propped up by what we often dismiss as vile; organisms that, if we peer past our visceral reactions, can be as fascinating as the most distant galaxies. I, for one, embrace this paradox and can confidently say that parasites do indeed reflect God’s goodness and display His handiwork.
References
- Selk A. "The extraordinary life and death of the world's oldest known spider." Washington Post. May 1, 2018. Retrieved Dec 4, 2025. https://www.washingtonpost.com/news/speaking-of-science/wp/2018/05/01/the-extraordinary-life-and-death-of-the-worlds-oldest-known-spider/
- Hudson PJ, Dobson AP, Lafferty KD. 2006. “Is a healthy ecosystem one that is rich in parasites?” Trends Ecol Evol. 21(7):381-385. doi: 10.1016/j.tree.2006.04.007.
- Bush SE, Villa SM, Altuna JC, Johnson KP, Shapiro MD, Clayton DH. 2019. “Host defense triggers rapid adaptive radiation in experimentally evolving parasites.” Evolution Letters. 3(2):120-128. doi: 10.1002/evl3.104.
Andrew Sweet is an Associate Professor of Evolutionary Biology at Arkansas State University. His research focuses on the evolution of birds, parasites, and genomes. He teaches courses in evolution, genetics, and zoology.