Where the male and female symbols came from…

May 30, 2015 by · Leave a Comment 

Representing two planets, iron, copper and a couple of Olympian gods, the classical symbols for male and female pack a lot of meaning into a few squiggly lines.

The symbols themselves are ancient, and the associations they make date back to the dawn of civilization. The ancients, after observing how the movements of heavenly bodies like the Sun and planets heralded a corresponding change in events on our planet, eventually came to believe that there was a causal relationship. Logically, then, ancient scholars began to study the heavens in order to better predict, and prepare for, the future. They also came to associate different heavenly bodies with their powerful gods- Mercury, Venus, Mars, Zeus (Jupiter) and Cronus (Saturn).

male and female

Each heavenly body, along with its god, was also associated with a particular metal. So, for example, the Sun (Helios) was associated with gold (note: in truth, the Sun is white in the human visual spectrum, not yellow); Mars (in Greek, Thouros) was associated with the hard, red metal used to make weapons, iron; and Venus (in Greek, Phosphorus) with the softer metal that can turn green, copper.

Writing about these metals, the Greeks would refer to them by their respective gods’ names, and then as now, these were spelled with a combination of letters; after awhile, a type of shorthand arose; for example, relevant to Mars (Thouros) and Venus (Phosphorus):

Mars (Thouros) and Venus (Phosphorus)In medieval times, European alchemists relied on these shorthand symbols, which were retained through the Enlightenment and used by such notables as Carolus Linnaeus (the father of modern taxonomy who made binomial nomenclature popular), to refer to such metals in his 1735 work Systema Naturae.

Linnaeus was also the first to use these signs in a biological context in his dissertation Plantae hybridae (1751), where he used the symbol for Venus to denote a female parent of a hybrid plant and the symbol for Mars to denote a male parent.

Linnaeus continued to use the symbols for the purpose of distinguishing male and female, and by 1753’s Species Plantarum, he was using the symbols freely [1]
Following in Linnaeus’ footsteps, other botanists incorporated the symbolism, as did scientists from other fields including zoology, human biology and, eventually, genetics.

Modern geneticists no longer use these familiar symbols and instead rely on a square (for male) and circle (for female):

Modern GeneticsThis symbolism was developed by Pliny Earle, a doctor with the Bloomingdale Asylum for the Insane in New York in 1845 while explaining the inheritance of color blindness:

For the purpose of clearly illustrating the prevalence of this physiological peculiarity in the family, I have prepared the subjoined genealogical chart. Males are represented by squares and females by circles.

While it is not entirely clear why Earle deviated from the classical symbols, one explanation was later given by Royal Society Member, Edward Nettleship, who claimed that Earle had been “unable to get any printer’s symbols capable of use . . . except those employed in printing music.”

This post has been republished with permission from TodayIFoundOut.com. Image by Daniel Chloe Blanchfield under Creative Commons license.

Why beetles have “hard” elytra?

March 6, 2015 by · Leave a Comment 

One of the most important features of Coleoptera is their ‘elytra’, the hard exoskeletal which covers their wings. The ‘elytra’ helps to protect the beetle but also has many other functions, too. Some beetles trap moisture in their wings and the elytra protects it from drying in heat and wind, this means the beetles can travel across arid deserts without dehydrating. Other Coleoptera can live under water because they can store air in their wings, which is again protected by the elytra. Coleoptera (beetles) are most probably the most versatile creatures on earth. The beetles exoskeleton is made up of numerous plates called sclerites (a hardened body part), separated by thin sutures. This design creates the armoured defenses of the beetle while maintaining flexibility.


The morphology of a fiddler beetle

Scientists interested in cuticle structure[1] have examined cuticle from the elytra of the red flour beetle, Tribolium castaneum. The elytra have two proteins in large amounts that are not present in the membranous hindwings. These proteins are associated with hard cuticle both in the elytra and elsewhere on the beetle. The cuticle of the elytra becomes hard and rigid from extensive crosslinking, or chemical connections between the protein strands. This evidence from red flour beetle suggests that in the evolutionary past, an ancestor of modern beetles had a mutation caused proteins for cuticle crosslinking to be expressed in the forewings. The up regulation of two cuticle genes in the forewings may be a key to the evolution of elytra.

The elytra are not used for flight, but tend to cover the hind part of the body and protect the second pair of wings. The elytra must be raised in order to move the hind flight wings. A beetles flight wings are crossed with veins and are folded after landing, often along these veins, and are stored below the elytra.


Cerymbycid beetle ready for takeoff [3]

In some beetles, the ability to fly has been lost. These include the ground beetles (family Carabidae) and some ‘true weevils’ (family Curculionidae), but also some desert and cave-dwelling species of other families. Many of these species have the two elytra fused together, forming a solid shield over the abdomen. In a few beetle families, both the ability to fly and the elytra have been lost, with the best known example being the glow-worms of the family Phengodidae, in which the females are larviform (where the females in the adult stage of metamorphosis resemble the larvae to various degrees) throughout their lives.

“Nature is replete with examples of layered-structure materials that are evolved through billions of years to provide high performance. Insect elytra (a portion of the exoskeleton) have evoked worldwide research attention and are believed to serve as fuselages and wings of natural aircraft. This work focuses on the relationship between structure, mechanical behavior, and failure mechanisms of the elytra. We report a failure-mode-optimization (FMO) mechanism that can explain elytra’s mechanical behaviors. We show initial evidence that this mechanism makes bio-structures of low-strength materials strong and ductile that can effectively resist shear forces and crack growth. A bio-inspired design of a joint by using the FMO mechanism has been proved by experiments to have a potential to increase the interface shear strength as high as about 2.5 times. The FMO mechanism, which is based on the new concept of property-structure synergetic coupling proposed in this work, offer some thoughts to deal with the notoriously difficult problem of interface strength and to reduce catastrophic failure events.” [2]


[1] Mi Young Noh, Karl J. Kramer, Subbaratnam Muthukrishnan, Michael R. Kanost, Richard W. Beeman, Yasuyuki Arakane. Two major cuticular proteins are required for assembly of horizontal laminae and vertical pore canals in rigid cuticle of Tribolium castaneum. Insect Biochemistry and Molecular Biology. 53: 22-29.

[2] Fan, J.; Chen, B.; Gao, Z.; Xiang, C. 2005. Mechanisms in Failure Prevention of Bio-Materials and Bio-Structures. Mechanics of Advanced Materials and Structures. 12(3): 229-237.

[3] Species 2000 & ITIS Catalogue of Life