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Originally mole-rats were likely the offspring of unrelated, monogamous parents (Hughes et al. 2008) and stayed in their natal nests because of ecological pressures. The benefit was a greater overall fitness because they did not have to face the dangers outside the nest, and the original cost was marginal, as reproductive rights had not yet been lost ( [link] ). Staying in the natal colony, however, reduced access to unrelated mates, which led to inbreeding. Reeve et al. (1990) found that today in naked mole-rat colonies more than 80% of matings that occur are either between siblings or between parents and offspring. Overall, these mole-rats have an average relatedness of 81% to their other colony members (Reeve et al. 1990) while average relatedness between full siblings is 50%.

As relatedness increased due to inbreeding and more individuals remained in the nest, a dominance hierarchy likely formed. The more dominant individuals held more reproductive rights. Gradually, the costs and benefits of staying changed slightly for non-breeders because of the inbreeding. The non-breeders gave up reproductive rights (the cost), thereby diminishing their direct fitness . However, they still had the benefit of avoiding outside dangers. More importantly, they gained greater indirect fitness because they were raising young highly related to them. In this manner they helped pass on their genes indirectly through the offspring of their relative, an act that added to their inclusive fitness. This inclusive fitness was greater on average than if they left to have their own young after the costs for leaving, such as predation and food risks, were taken into account.

Fortress defense and the aridity food distribution hypothesis

Fortress defense and the Aridity Food Distribution Hypothesis are two different hypotheses that use extrinsic factors to explain part of the cause of the rise of eusociality. The fortress defense theory holds that eusociality evolved in order to avoid predation (Queller and Strassmann 1998). Fortress defenders are unique from other social organisms in that they nest and feed within an area protected from predators. In addition, the food they eat is not well distributed. These combined factors favor staying in a safe location with access to food over the risks of leaving and reproducing (Alexander et al. 1991, Queller and Strassmann 1998).

A climate map of Africa.
This is a simplified climate map. Heterocephalus glaber and Cryptomys damarensis are found in the arid regions of the Kalahari Basin, the Horn of Africa, and southwestern Africa.

The Aridity Food Distribution Hypothesis, the second theory based on extrinsic factors, states that eusociality in H. glaber and C. damarensis evolved due to selective pressure from the arid environment that they both inhabit (Faulkes et al. 1997b, [link] ). According to Jarvis et al. (1998), mole-rats find the dry soil of their habitats hard to dig, a constraint that increases their energetic expenses in efforts to obtain resources. These habitats have sporadic rainfall and high evaporation rates ( [link] ), so there is a limited time period in which to work after the rain has stopped before the ground is too hard again (Jarvis et al. 1998). Mole-rat colonies maximize the number of members for cooperative foraging and group living so that after a rainfall they can better exploit the short time they have and reduce the risks of failure in foraging ( [link] ). The two hypotheses examine the ecological factors involved in the evolution of eusociality. Intrinsic factors, such as hormone regulation, however, are also involved.

Questions & Answers

Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
yes that's correct
I think
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
analytical skills graphene is prepared to kill any type viruses .
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
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Source:  OpenStax, Mockingbird tales: readings in animal behavior. OpenStax CNX. Jan 12, 2011 Download for free at http://cnx.org/content/col11211/1.5
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