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Getting an evolutionary handle on life after reproduction
December 27, 2005Since many animals live beyond their fertile years, biologists have searched for evolutionary clues to this extended lifespan. What role, if any, does natural selection play in the evolution of the postreproductive lifespan? For natural selection to shape the twilight years, postreproductive females should contribute to the fitness of their offspring or relatives, a hypothesis called the "grandmother effect." Though many mammals, including lions and baboons, rear dependent young and operate within complex social groups, studies have found no evidence of a granny effect, and females mostly live just long enough to care for their last born. For nonsocial animals that spawn independent young, extended lifespan is associated with good nutrition and the absence of disease and predators.
In a new study, David Reznick, Michael Bryant, and Donna Holmes provide the first experimental confirmation that evolution works selectively on those aspects of life history that directly affect fitness. They expand on their ongoing investigations of the life history of guppies confronting different predatory threats in Trinidad. Individuals facing different mortality threats should evolve different adaptations in their life histories, such as age at first reproduction, investment in reproduction, and patterns of senescence, including declines in reproduction. Since guppies are livebearers that provide no postnatal maternal care, Reznick et al. predicted the populations would show no differences in postreproductive lifespan-which is what they found.
Though overall lifespan varied among the populations, these variations stemmed from differences in time allotted only to reproduction. Postreproductive lifespan, in contrast, showed no signs of being under selection, and appeared to be what the authors called a "random add-on at the end of the life history." Random or not, this is the first demonstration of a postreproductive lifespan in fish.
These findings also refute the suggestion that fish may experience little or no reproductive senescence based on evidence that they continue to produce eggs as adults. It's an open question whether postreproductive lifespan can influence fitness enough to be under selection. But in a field dominated by investigations into the origins of human menopause and extended lifespan, the authors make a strong case for using experimental comparative analyses of other species to gain an evolutionary perspective on the human condition.
Public Library of Science
These findings also refute the suggestion that fish may experience little or no reproductive senescence based on evidence that they continue to produce eggs as adults. It's an open question whether postreproductive lifespan can influence fitness enough to be under selection. But in a field dominated by investigations into the origins of human menopause and extended lifespan, the authors make a strong case for using experimental comparative analyses of other species to gain an evolutionary perspective on the human condition.
Public Library of Science
Lifespan Current Events and Lifespan News RSSScientists find molecular trigger that helps prevent aging and disease
Researchers at Mount Sinai School of Medicine set out to address a question that has been challenging scientists for years: How do dietary restriction-and the reverse, overconsumption-produce protective effects against aging and disease?
New UAB Study Sheds Light on Brain's Response to Distress, Unexpected Events
In a new study, psychologists at the University of Alabama at Birmingham (UAB) are able to see in detail for the first time how various regions of the human brain respond when people experience an unexpected or traumatic event.
Reduction in glycotoxins from heat-processing of foods reduces risk of chronic disease
Researchers from Mount Sinai School of Medicine report that cutting back on the consumption of processed and fried foods, which are high in toxins called Advanced Glycation End products (AGEs), can reduce inflammation and actually help restore the body's natural defenses regardless of age or health status.
Common weed could provide clues on aging and cancer
A common weed and human cancer cells could provide some very uncommon details about DNA structure and its relationship with telomeres and how they affect cellular aging and cancer, according to a team led by scientists from Texas A&M University and the University of Cincinnati (UC).
Puberty a gateway to heart disease for Canada's teens
A seven-year ongoing study examining over 20,000 Canadian grade 9 students shows most already have at least one major risk factor for heart disease and stroke, Dr. Brian McCrindle told the Canadian Cardiovascular Congress 2009, co-hosted by the Heart and Stroke Foundation and the Canadian Cardiovascular Society.
Exon-skipping drug prevents muscle wasting, maintains muscle function in dystrophin deficient mice
An exon skipping PPMO has demonstrated dramatic effects in the prevention and treatment of severely affected, dystrophin and utrophin-deficient mice, preventing severe deterioration of the treated animals and extending their lifespan.
Better blood screening process needed to prevent babesiosis transmission
Babesiosis is a potentially dangerous parasitic disease transmitted by ticks and is common in the Northeast and the upper Midwest. Babesia lives inside of red blood cells, meaning it can also be transmitted through a blood transfusion from an infected but otherwise asymptomatic blood donor.
Compound shows potential for slowing progression of ALS
A chemical cousin of a drug currently used to treat sepsis dramatically slows the progression of amyotrophic lateral sclerosis, better known as ALS or Lou Gehrig's disease, in mice.
Suppressing a gene in mice prevents heart from aging, preserves its function
Scientists prevented age-related changes in the hearts of mice and preserved heart function by suppressing a form of the PI3K gene, in a study reported in Circulation: Journal of the American Heart Association.
Amyotrophic lateral sclerosis may involve a form of sudden, rapid aging of the immune system
Premature aging of the immune system appears to play a role in the development of amyotrophic lateral sclerosis (ALS), or Lou Gehrig's disease, according to research scientists from the Maxine Dunitz Neurosurgical Institute at Cedars-Sinai Medical Center, the Weizmann Institute of Science in Israel, and Sheba Medical Center in Israel.
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LifeSpan Fitness VP-1000 Vibration Plate by LifeSpan Fitness Enjoy the benefits of whole body vibration using the LifeSpan VP1000 Vibration Plate. Its dual-motion design encompasses an up/down pivoting system and a secondary front/back pivot. The result is a multi-dimensional platform movement that enhances the benefits you'll receive from whole body vibration, including improved muscle strength, balance and flexibility. In addition to standing in an upright position, there are many other uses of the vibration plate to increase your physical activity and improve your strength, including calf stretches, lunges, squats, pushups, sit-up twists and tricep dips. Assembly is required. How It Works |
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LifeSpan Fitness 100% Silicone Treadmill Belt Lubricant by LifeSpan Fitness LifeSpan 100% silicone treadmill lubricant improves your treadmills performance and prevents costly repairs. The LifeSpan lubricant contains NO odors, NO propellants and NO distillates. The lubricant was created to service all treadmills that utilize a silicone based lubrication system. The pump sprayer provides the user a universal applicator for easy application. Silicone comes in a 4 oz bottle that provides (1) year worth of applications. |
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