Arms Race of Survival

 Arms race of survival 

Figure 1: Neanderthal [6]

 

The picture above shows a speculative reconstruction of a Neanderthal male, a subspecies of modern humans believed to have lived in Europe in the colder climates. The physical features of Neanderthals appear to give them much more physical strength than our own species of Homo Sapiens as they had bulkier bodies and larger heights than ours. Yet, our species is believed to have been the cause of their extinction. This fact of nature tells us a lot about how evolution and survival work to fine-tune the cycle of life on earth. The ability to survive and evolve is not proportional to the strength and physical capabilities. Survival is only guaranteed to those who adapt to equip themselves and respond to change rapidly. In the case of Neanderthals and our subspecies of Homo Sapiens, our better cognitive ability turned out to be a better tool than the physical strength of neanderthal for better adaptations. 

Our own species was able to figure out how to control and grow plants and raise animals for their own survival with the invention of farming. Millions of years ago, our hunter-gatherer ancestors gathered up in groups to form one of the earliest civilizations which eventually led us to be at the top of the food chain. But, we have had our fair share of famines and disease outbreaks that wiped off a huge number of humans. Till this point, we have been able to survive and strengthen our defences especially with medicine and no other animal, let alone plant species has been able to launch an effective counteroffensive against us despite our cruelties against them. The Happening is a movie that visits such a hypothetical apocalyptic event where plants are shown to have launched a counteroffensive against humans due to their overexploitation. The plants are shown to release a toxin that reverses our survival extinct and forces entire populations to commit suicide within minutes. In this blog, I would like to talk about the science of such interesting mutations and defence mechanisms of plants. Let us start from something that the movie did not talk about but is something really interesting to see how much plants can evolve far from their usual characteristics to ensure their survival.

           Hunter plants

Figure 2:Sarracenia, Nepenthes, and Cephalotus (left to right) [1]

 

The picture above shows three species of carnivorous plants known as Sarracenia, Nepenthes, and Cephalotus which evolved independently in American, Asian and Australian continents. These plants are commonly known as pitcher plants but they do not hold any ancestral linkages despite their similar characteristics and behaviour. These plants are known to have evolved in nutritionally poor soils which forced them to search for alternative sources of essential plant nutrients from insects. Genome analysis of these plants suggests that they adapted the proteins usually used to fight plant diseases to digest the hard exoskeleton of insects [1]. Similarly, carnivorous plants maxed out the nutrient absorption capability of leaves to suck in the nutrients of insects [1]. Out of the three species mentioned above, the Sarracenia is found in the seasonally wet grasslands which are highly acidic which is a hostile environment for normal plants. The Sarracenia plant that survived and continues to survive in such environments has beautifully equipped itself to capture insects and conserve rainwater in its funnel-like leaves. These numbers of mutations allow Sarracenia and all other carnivore plants to survive in challenging climates where other plants must have died down and lost the race for survival. Despite their interesting evolution, the carnivorous plants are least likely to ever pose a threat to humans directly.

Silent Killers

Figure 3: Poisnous Hemlock Plant [7]

For millions of years, plants and their predators have been up against each other in an arms race of evolution. The plants are continuously attacked by herbivore animals that consume their leaves and in response, future plant generations mutate their chemistry or characteristics to defend themselves and the cycle continues as each species evolves to outsmart the next [2]. Examples of such mutations are found in plants with an extreme taste such as the mustard plant and poisonous plants such as the hemlock [2]. While such plants can cause damage to a human body, they require voluntary consumption and such defences are actually meant for herbivore animals only.

 

    Plants against Humans?

Figure 4: Scene from movie "The Happening"

                                            

Now, we turn to plant toxins that were also the main science behind the movie too. It is a well-researched fact that plants can release airborne toxins in order to alarm neighbouring plants and create an attack on a potential predator [3]. Plants can also release harmful chemicals against other plants to compete for nutrients in the soil. But, the effects of any such toxins or harmful chemicals are not known to have caused major issues to human health especially when it comes to changing the brain chemistry of a human. It should be noted that just because such a toxin is not known, it is within the realm of possibilities that plants may evolve to produce some seriously damaging toxin against humans [4].

The movie also stretches the strength of plant communication as if they had some good sense of consciousness. Plants can communicate with each other to warn against potential predators but that does not mean as if there is a sense of conscious communication amongst the plants [4].

The movie does make an interesting reference to the phenomenon of ‘red tide’.This phenomenon is usually observed when colonies of algae overpopulate the ocean and releases toxins that are not just harmful but lethal to fishes, shellfish, marine mammals, and birds [5]. While red tides can be harmful to humans too but their occurrence is seen to be caused by nutrient pollution which encourages the growth of such algae in excess. It is not counter-offensive either contrary to what the movie claimed[4].

Figure 5: Red Tide [8]

References:

1. Fukushima, K., Fang, X., Alvarez-Ponce, D. et al. Genome of the pitcher plant Cephalotus reveals genetic changes associated with carnivory. Nat Ecol Evol 1, 0059 (2017). https://doi.org/10.1038/s41559-016-0059

2. On the defence. Florida Museum. (2019, May 3). Retrieved November 29, 2021, from https://www.floridamuseum.ufl.edu/science/on-the-defense/. 

3. Accesspharmacy.mhmedical.com. 2021. Toxic Effects of Plants and Animals | Casarett & Doull’s Essentials of Toxicology, 3e | AccessPharmacy | McGraw Hill Medical. [online] Available at: <https://accesspharmacy.mhmedical.com/content.aspx?bookid=1540&sectionid=92528244> [Accessed 29 November 2021].

4. Nast, C., 2021. The Happening: Science Fact or Science Fiction?. [online] Wired. Available at: <https://www.wired.com/2008/06/the-happening-s/> [Accessed 29 November 2021].

5. US Department of Commerce, N. O. and A. A. (2013, June 1). What is a red tide? NOAA's National Ocean Service. Retrieved November 29, 2021, from https://oceanservice.noaa.gov/facts/redtide.html. 

6. Discover Magazine. 2021. Homo Longi: Extinct Human Species That May Replace Neanderthals As Our Closest Relatives Found in China. [online] Available at: <https://www.discovermagazine.com/planet-earth/homo-longi-extinct-human-species-that-may-replace-neanderthals-as-our> [Accessed 29 November 2021].

7. Healthline. 2021. Hemlock Poisoning: Symptoms, Treatment, and Prevention. [online] Available at: <https://www.healthline.com/health/hemlock-poisoning> [Accessed 29 November 2021].

8. Youtube.com. 2021. [online] Available at: <https://www.youtube.com/watch?v=WnbtVFvZcqA> [Accessed 29 November 2021].

9. HAPPENING, T. and Shyamalan, M., 2021. The Happening. [online] MUBI. Available at: <https://mubi.com/films/the-happening> [Accessed 29 November 2021].