WASHINGTON – Women live longer than men across the world and scientists have by and large linked the sex differences in longevity with biological foundation to survival. A new study of wild mammals has found considerable differences in life span and aging in various mammalian species.
Among humans, women’s life span is almost 8% on average longer than men’s life span. But among wild mammals, females in 60% of the studied species have, on average, 18.6% longer lifespans. The ratio is considerably different for different groups of mammals.
An international team of scientists led by Jean-François Lemaître, from the University Lyonin France, collected information on age-related mortality for 134 populations of 101 wild mammalian species.
“It was surprising to observe that this gender gap in lifespan often exceeds the one observed in humans and is, at the same time, extremely variable across species,” said Lemaître.
“For example, lionesses live at least 50% longer in the wild than male lions,” said Tamás Székely, from the University of Bath, one of the authors of the study.
“We previously thought this was mostly due to sexual selection – because males fight with each other to overtake a pride and thus have access to females, however our data do not support this,“ said Székely.
Scientists have found that even though females consistently live longer than males, the risk of mortality does not increase more rapidly in males than in females across species. Therefore, they say, there must be other, more complex factors at play, such as environmental conditions in which the animals live and sex-specific growth, survival and reproduction through the history of the species.
For example, the authors of the study say, roaming males could be exposed to more environmental pathogens. This was noticed in three populations of the bighorn sheep.
The magnitude of the lifespan gap could also be shaped by local environmental conditions with a trade-off between reproduction and survival. In some species, males allocate more resources to sexual competition and reproduction, which, scientists say, could lead to bigger sex differences in lifespans.
“Another possible explanation for the sex difference is that female survival increases when males provide some or all of the parental care,“ said Székely. “Giving birth and caring for young becomes a significant health cost for females and so this cost is reduced if both parents work together to bring up their offspring.”
In order to measure the extent to which biological differences between the sexes affect life expectancy, scientists plan to compare the data on wild mammals with the data on mammals kept in the zoo, where they do not have to fight with predators or compete for food and mates.
Scientists hope the findings will contribute to better understanding of what affects human longevity. In the past 200 years, the average life expectancy of humans has more than doubled due to improved living conditions and advances in medicine. Yet women continue to live longer than men, suggesting the biological differences also have a role.
According to the U.S. Centers for Disease Control, the average American man will live to age 76, while the average woman in America will live to age 81. Women can also expect to be healthier than men in their senior years. Experts shave said the gap is due to a combination of biological and social differences.
Men’s hormone testosterone is linked to a decrease in their immune system and risk of cardiovascular diseases as they age. It is also linked to risky behavior: smoking, drinking and unhealthy eating habits. If diagnosed, men are less likely than women to follow doctor’s advice. Statistics show that men are more likely to take life-threatening risks and to die in car accidents, or gun fights.
Authors of the new study say the differences between male and female longevity are shaped by complex interactions between local environmental conditions and sex-specific reproductive biology. They say that more research is likely to provide “innovative insights into the evolutionary roots and physiology underlying aging in both sexes.”
Mercury-bound spacecraft buzzes Earth, beams back pictures – CityNews Edmonton
CAPE CANAVERAL, Fla. — A Mercury-bound spacecraft swooped past Earth on Friday, tweaking its round-about path to the solar system’s smallest and innermost planet.
Launched 1 1/2 years ago, Europe and Japan’s Bepi-Colombo spacecraft passed within 8,000 miles (12,700 kilometres) of Earth. The closest approach occurred over the South Atlantic, with telescopes in Chile catching a glimpse of the speeding spacecraft.
The gravity tug from Earth slowed Bepi-Colombo and put it on a course closer to the sun.
It was the first of nine planetary gravity assists — and the only one involving Earth — on the spacecraft’s seven-year journey to Mercury. The spacecraft — comprised of two scientific orbiters — should reach Mercury in 2025, after swinging twice past Venus and six times past Mercury itself. The next flyby will be at Venus in October.
Before leaving Earth’s vicinity, Bepi-Colombo beamed back black-and-white pictures of the home planet. The spacecraft holds three GoPro-type cameras.
“These selfies from space are humbling, showing our planet, the common home that we share, in one of the most troubling and uncertain periods many of us have gone through,” Gunther Hasinger, the European Space Agency’s science director, said via Twitter.
The space agency’s control centre in Germany had fewer staff than usual for Friday’s operation because of the coronavirus pandemic. The ground controllers sat far apart as they monitored the flyby. Data from the flyby will be used to calibrate Bepi-Colombo’s science instruments.
Scientists hope to learn more about the origin and composition of Mercury, once the European and Japanese orbiters separate and begin their own circling of the scorched planet.
Mercury is the least explored of our solar system’s four rocky planets. It’s just a little bigger than our moon and circles the sun in just 88 days.
The spacecraft is named after Italian mathematician and engineer Giuseppe “Bepi” Colombo, who devised the use of planetary flybys for Mercury encounters. He died in 1984.
The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Department of Science Education. The AP is solely responsible for all content.
Marcia Dunn, The Associated Press
50 years after Apollo 13, we can now see the moon as the astronauts did – Space.com
This Saturday (April 11) will mark 50 years since NASA’s Apollo 13 mission launched on an unexpectedly tumultuous journey around the moon. Now, a modern lunar orbiter has reconstructed what the Apollo 13 astronauts would have seen of the lunar surface.
Famously described as a “successful failure,” Apollo 13 did not go as planned: An oxygen tank exploded 56 hours into the mission. Thankfully, some fast-thinking teamwork between the astronauts and mission control back on Earth salvaged the mission and, after a trip around the moon, the astronauts safely returned to Earth.
So, while the crew didn’t land on the moon as planned, they did travel around it and, thanks to modern technology, we can now see what they saw on this journey.
A photo of the lunar surface taken by the Apollo 13 astronauts on their trip around the moon.
Soon after sunrise, the Apollo 13 crew snapped this incredible shot of the moon.
A snapshot of the Tsiolkovskiy crater, taken by the Apollo 13 crew with a telephoto lens.
Researchers used data from NASA’s Lunar Reconnaissance Orbiter mission to recreate what the Apollo 13 crew saw as they flew around the far side of the moon. In the video, you can see craters and other lunar features emerge from the darkness. You can imagine yourself as any of the crewmembers — commander Jim Lovell, command module pilot Jack Swigert or lunar module pilot Fred Haise — looking down and watching the lunar surface pass by as the spacecraft flew overhead.
In addition to the Lunar Reconnaissance Orbiter data, the researchers also consulted the Apollo 13 flight plan and, despite the major change in plans with the mission, were able to use the position and speed at the craft’s closest point to the Moon which was listed in the Apollo 13 Mission Report. Taken together, those details allowed them to determine factors including the position and speed of the spacecraft at its closest point to the moon, which helped clarify the vehicle’s trajectory.
To create this virtual trip around the moon, this team was also informed by photos taken by the Apollo 13 crew during this trip around the moon. You can see some of the captivating original images above, but you can also find every Apollo 13 photo ever online in the Apollo Image Atlas.
Shine on, shine on – Skywatching – Castanet.net
The moon is unusual. There are bigger moons in the Solar System, some with under-ice oceans and at least one with a thick atmosphere.
However, all those other moons orbit giant planets.
Our moon is so large compared with the Earth that sometimes the pair get described as a double planet.
This suggests that something happened that differs from what went on in the young Solar System, when the planets formed.
The standard picture is the collapse of a cloud of gas and dust into a rotating disc. The core forms a star, the Sun, the disc forms smaller discs that collapse into planets, and the left over material forms moons, all far smaller than the planet.
There is a limit to how small one of these collapsing discs can be because the body in the centre has to have enough gravity to hold it together, and with lots of bodies forming nearby, all their conflicting gravitational attractions cause small discs to dissipate.
The moon is too big to be a by-product of the Earth’s disc and too small to have a disc of its own. So, where did it come from?
One suggestion was that the young Earth was spinning too quickly to hold itself together and spun off the moon.
The theory that seems to best fit the bill as we see things at present is that soon after the Earth formed it was hit by an object around the size of Mars. The resulting chaotic debris then collapsed to form the Earth and moon.
The “pre-Earth” was a fully formed planet when it was hit. Heavy elements such as iron and nickel had settled down into the centre, forming the core, and the material surrounding it, volcanic rocks such as basalt formed a mantle.
This stuff was semi-molten, as it is today, with a cooler, solidifying surface of basalt rocks, rather like the floor of our oceans today. The impact was unlikely to have been dead centre, because the debris cloud would have been thrown off so fast it would never fall back to form only one or two bodies.
An off-centre impact would have removed a large lump of the pre-Earth’s mantle and a bit of core. This agrees with the geological information and the rock samples brought back from the moon by the Apollo astronauts.
The moon ‘s rocks are very much like the basaltic rocks making up the Earth’s ocean floor and mantle. The main difference is that the rocks the astronauts managed to grab were from the moon ‘s surface, and have been exposed to billions of years of vacuum and hot and cold, and as a result are extremely dry.
After things settled down again, we had a young Earth that rotated faster than it does today, and the moon orbited much closer. The two worlds pulled up huge tides in each other, and the rapid rotation of the Earth pulled the tidal bulge a bit ahead of the moon.
The gravitational pull of the bulge pulled at the Moon, speeding it up, and perversely, the way orbits work is that trying to speed an object up makes its orbit move further away and makes it move slower.
Try swinging a ball around your head on the end of a couple of metres of elastic. Once you have it moving in a nice circle, try to speed it up. It will move away and slow down. This is definitely a “do outdoors and use eye protection experiment.” Believe me, I’ve done it.
While the pull of the tidal bulge accelerated the moon, it slowed the Earth’s rotation, so that today our day is 24 hours long. This tidal process has not finished.
The moon is still receding from us, and our days are still lengthening.
One consequence of this is that one day there will no longer be any total eclipses of the Sun.
That our moon is at the right distance from us to exactly cover the Sun is probably unique in our galaxy, and this lucky coincidence won’t last forever.
- Venus shines brightly in the west after sunset
- Left to right, Mars, Saturn and Jupiter lie close together low in the southeast before dawn
- The moon will reach Last Quarter on the 14th.
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