Analysis of sex specific genetic material, the non-recombining portions of the Y chromosome and mitochondrial DNA, show evidence of a prevalence of female-biased dispersal as well; however, these results could also be affected by the effective breeding numbers of males and females in local populations. Evidence of female-biased dispersion in hunter-gatherers is not definitive, with some studies supporting the idea, and others suggesting there is no strong bias towards either sex. In orcas, both sexes mate non-locally with members of a different pod but return to the pod after copulation. Demographic data shows that a females mean relatedness to the group does increase over time due to increasing relatedness to males. While less well-studied, there is evidence that short-finned pilot whales, another menopausal species, also display this behavior. However, mating behavior that increases local relatedness with female age is prevalent in non-menopausal species, making it unlikely that it is the only factor that determines if menopause will evolve in a species. Mother hypothesis
The mother hypothesis suggests that menopause was selected for humans because of the extended development period of human offspring and high costs of reproduction so that mothers gain an advantage in reproductive fitness by redirecting their effort from new offspring with a low survival chance to existing children with a higher survival chance. Grandmother hypothesis
The grandmother hypothesis suggests that menopause was selected for humans because it promotes the survival of grandchildren. According to this hypothesis, post-reproductive women feed and care for children, adult nursing daughters, and grandchildren whose mothers have weaned them.
Sphingolipidoses are a class of lipid storage disorders or degenerative storage disorders caused by deficiency of an enzyme that is required for the catabolism of lipids that contain ceramide, also relating to sphingolipid metabolism. The main members of this group are Niemann–Pick disease, Fabry disease, Krabbe disease, Gaucher disease, Tay–Sachs disease and metachromatic leukodystrophy. They are generally inherited in an autosomal recessive fashion, but notably Fabry disease is X-linked recessive. Taken together, sphingolipidoses have an incidence of approximately 1 in 10,000, but substantially more in certain populations such as Ashkenazi Jews. Enzyme replacement therapy is available to treat mainly Fabry disease and Gaucher disease, and people with these types of sphingolipidoses may live well into adulthood. The other types are generally fatal by age 1 to 5 years for infantile forms, but progression may be mild for juvenile- or adult-onset forms. Accumulated products
Gangliosides: Gangliosidosis
GM1 gangliosidoses
GM2 gangliosidoses
Tay–Sachs disease
Sandhoff disease
GM2-gangliosidosis, AB variant
Glycolipids
Fabrys disease
Krabbe disease
Metachromatic leukodystrophy
Glucocerebrosides
Gauchers disease

Comparison
Metabolic pathways
See also
Lipid storage disorder

References
External links

Sphingolipidoses at the US National Library of Medicine Medical Subject Headings (MeSH)