Is sex primarily a strategy against transmissible cancer?

Is sex primarily a strategy against transmissible cancer?
By blending genetics, sexual reproduction produces greater genetic diversity in a population, limiting the transmission of cancer cells across individuals in the population. This genetic diversity facilitates detection of the invading non-self cells and also limits the chances that the transmissible cancer cells are preadapted to the new host. Thus, cancer cells regularly emerge in individuals, but often malignant cells fail to be transmitted. Credit:

PLOS Biology , 10.1371/journal.pbio.3000275

One of the greatest enigmas of evolutionary biology is that while sex is the dominant mode of reproduction among multicellular organisms, asexual reproduction appears much more efficient and less costly. However, in a study publishing on June 6 in the open-access journal PLOS Biology, researchers suggest that sexual reproduction is favored by selection because, unlike asexual reproduction, it not only provides important evolutionary advantages in constantly changing environments, but also prevents the invasion of transmissible cancer, or "cheater" cells.

Multicellular organisms are societies of cooperating clonal cells that emerged and evolved one billion years ago. A key point in the evolution of multicellular organisms was therefore the ability to prevent cheater cells from overexploiting the cooperative system; this evolutionary constraint favoured the emergence of the many known mechanisms that suppress cancer, notably the . Whatever the efficiency of these mechanisms, a prerequisite of all these defences is the ability to recognize cheater cells from normal ones.

Not only did first multicellular organisms have to deal with their own cheater cells, they also had to evolve adaptations to prevent them being colonized by foreign malignant cells (i.e. infectious ones). Because leads to identical ("clonal") organisms, this mode of reproduction is risky due to the possibility of being invaded by clonal infectious cell lineages (i.e. transmissible cancers). Conversely, decreases the compatibility of contagious cancer cells with their hosts, limiting individual infection risk, as well as the risks of transmission between parent and offspring. Sexual reproduction also generates that facilitates the detection of foreign cells, the first and critical step of immune protection.

Although relatively rare, transmissible cancers do exist (e.g. Tasmanian devils, dogs, bivalves), and increasing evidence suggests that most, if not all, malignant cells are potentially transmissible provided a suitable transmission route is offered. Given the ubiquity of cancer in , in combination with the plethora of potential transmission routes, sexual reproduction may have been favoured as a less risky, more profitable option to produce viable offspring despite its associated costs.

The authors claim that to their knowledge, the proposed role of transmissible cheater cells as initiator and driver force underlying the evolution of sexual reproduction is a novel explanation, that will contribute to a paradigm shift in our understanding of evolution.


Explore further

Biologists identify influence of environment on sexual vs. asexual reproduction

More information: Thomas F, Madsen T, Giraudeau M, Misse D, Hamede R, Vincze O, et al. (2019) Transmissible cancer and the evolution of sex. PLoS Biol 17(6): e3000275. doi.org/10.1371/journal.pbio.3000275
Journal information: PLoS Biology

Citation: Is sex primarily a strategy against transmissible cancer? (2019, June 6) retrieved 24 July 2019 from https://phys.org/news/2019-06-sex-primarily-strategy-transmissible-cancer.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
358 shares

Feedback to editors

User comments

Jun 06, 2019
Sex unfortunately promotes the spread of social cancer. My daughter for example is definitely a cancerous parasite on the rest of my family.

j/k

Jun 06, 2019
Asexual reproduction should limit the possibilities in regard multicellular life forms to balls of goo.

Have I just not been paying attention?

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more