Inbreeding is the mating of closely related individuals. Inbreeding not only affects populations in nature but also has significant consequences for human populations. While the effects of inbreeding are decreasing in today’s mobile human world, in naturally occurring populations inbreeding is still easily possible.
Additionally, human society has encouraged inbreeding in some popular domesticated species like cats and dogs. The stigma inbreeding carries in modern culture is due both to commonly held moral beliefs and the higher probability of detrimental genetic disorders and diseases being passed on to successive generations.
Inbreeding Decreases Genetic Diversity
Basic genetics states that traits are hereditary. In other words, characteristics are passed from parent to offspring. Typically, if both parents have the same trait (ex. blue eyes, brown hair, connected earlobes) the likelihood of their offspring having that trait increases. In populations with a high amount of inbreeding, traits will become gradually more common. If this trait is beneficial, the population will likely continue to use it to their evolutionary advantage. However, inbred traits are generally detrimental to populations because these lower survivability and fertility. With shorter lifespans and fewer successful births, the population will either remain at dangerously low numbers or die.
Genetic diversity promotes survival. Although it is important to note situations during which inbred traits can momentarily promote the survivability of a species, populations cannot evolve or adapt to new conditions easily without diversity. Genetic diversity protects against populations succumbing to changing environments and various diseases and disorders.
How Inbreeding Increases Genetic Diseases and Disorders
Genetic diseases and disorders are often caused by recessive genes. These genes do not necessarily cause harmful traits in offspring. Instead, they are labeled recessive because both parents (the sperm and egg) must pass on the trait for the offspring to show the trait. In contrast, traits which only have to be passed on to offspring by one parent in order to be displayed are called dominant. Traits are not always outwardly physical like hair and skin color. They can also be developmental like weak hip joints or vision issues.
During inbreeding, two closely related individuals who mate have a much higher chance of passing on the same recessive traits. Since these traits are often associated with harmful diseases or disorders, offspring from inbred mating have greater chances of living with debilitating issues
The Consequences of Inbreeding in the African Cheetah
Smaller, more crowded populations have higher percentages of inbreeding. The cheetah of Africa has seen several genetic bottlenecks during the history of its species. Having endured the Ice Age 10,000 years ago, decreasing suitable habitat, and the intense hunting of nineteenth-century farmers and game hunters, the cheetah, has very low genetic diversity in small populations across Africa’s nature preserves. With centuries of inbreeding, the Cheetah’s genetic diversity resembles that of a lab rat whose genetic uniformity is important to experimental science.
The potential for disease in cheetah populations is an imminent threat to the survival of the species. To offset the low genetic diversity and crowded conditions, conservationists are implementing captive breeding programs to ensure healthy offspring. Successful programs will need to mate cheetahs from different populations and promote genetic diversity which will ensure the cheetah adaptability to changing climates and human demands.