Roses protect itself with sharp thorns, viruses pierce cell walls with spines and narwhals use a long tusk. Scientists concluded by comparing the length, diameter, and stability of the structures that although these pointed structures differ in size by several orders of magnitude, they are nevertheless all built on the same principle. But Why do some plants and animals have thorns and spines and what is the principle they are based upon? Let’s find out.

Why Plants Have Thorns
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Why Do Some Plants And Animals Have Thorns And Spines?

Spines, thorns, tusks, or prickles are an evolutionary adaptation by plants to protect themselves from their predators. However, there are some other uses of the tusks in the animal kingdom. They can be used to fight predators as well as finding a suitable mate. Even in plants, some thorns have either poison or irritating agents to fend off the predators furthermore. In cactus, apart from defending the plant, thorns also help in restricting the airflow as well as providing shade to prevent water loss. 

However, it is still debatable, what made these plants and animals develop a sword from within to fight for life. Also, several theorists doubt that it is an evolutionary development. According to them, a brain or some form of thought process is required to develop such abilities. Nevertheless, the real reason is yet to be discovered.

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The Basis of The Thorn Design

Scientists first analyzed various spines and thorns from the flora and fauna. Based on values, the researchers compared the diameter of the spike base with the respective spike length. Accordingly, the length of the spines, thorns, or tusks varied between forty nanometers and four and a half meters. However, the same mathematical connection applies to all structures. They are approximately 17 times longer than the diameter of their respective circular bases.

Why Do Animals and Plants Have Thorns
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Researchers also compared the stability of the spines and thorns. The natural structures are usually just stable enough to fulfill their purpose. For example, a virus can penetrate the cell wall of a cell and a mosquito can penetrate a person’s skin.

This comparison of the so-called elastic modulus, which is a value for the stability during bending, showed that all spines and thorns can be described with the same mathematical equation. The design of the pointed structures is very similar, from the nano-sting of a virus to the so-called spike of a swordfish.

The biophysicists not only examined natural thorns and spines. They also supplemented medical needles, nails, and historical lances made by humans in their comparative study. Even these pointed structures largely obey the equation they have drawn up.

Why Animals Have Thorns
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However, historical weapons were somewhat less stable, modern injection needles were much more stable than the ideal value calculated in each case. These new findings can be used to calculate the optimal design of a pointed object. In the future, the use of materials can be reduced without sacrificing the required stability.

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