- 9 hours ago
Sperm counts in men worldwide have dropped dramatically in the last 50 years. What could be causing it? Also: determining dolphin sex, breeding ozone resistant rice, and an equation for estimating alien civilizations.
Category
🗞
NewsTranscript
00:06Many couples want children, but sometimes it just doesn't happen.
00:10And while infertility is often seen as a female issue, it's frequently linked to sperm quality.
00:18Globally, sperm counts have dropped by about half over the past 50 years.
00:24So could environmental factors be playing a role?
00:28A new Swiss study suggests that where men live, in a city or countryside, could make a difference.
00:39All that and more, coming up on DW Science Show.
00:44Welcome to Tomorrow Today.
00:50Hello, hello.
00:50Hello, Florian Schisser is a carpenter and woodworker who set up his shop not far from the city of Bern
00:56in Switzerland.
00:57And a fast fertiger woman.
01:19You would have to confront your witnesses
01:23or be confronted with things that aren't cool
01:25and that you don't want everyone to know.
01:31For years, Florian and his wife tried to conceive naturally,
01:36without success.
01:38After seeking medical advice,
01:40they discovered he was infertile.
01:45The reporter asked what it felt like
01:48when he got the first results,
01:50when he heard that it was because his sperm
01:52just wasn't up to the task.
01:55He replies that it was devastating
01:57and caused a huge amount of uncertainty.
02:00They didn't know what came next,
02:02and a bigger question was,
02:05he thought, if she wants children
02:07but can't have them with me,
02:09I have to let her go.
02:10And that was harder than the fact of infertility itself.
02:18In Switzerland, an estimated one in six couples is childless
02:23and not by choice.
02:25In over a third of those cases,
02:27it's due to poor sperm quality.
02:31We head to the University of Geneva
02:34and the lab of Switzerland's leading researcher in the field.
02:37Rita Rabban has studied sperm quality in men from the Alpine country for years.
02:44There's many things that are actually fascinating about the sperm.
02:49It's the only cell in the human body that exerts its function outside of where it was produced.
02:56The female reproductive tract is very hostile,
02:58the vagina is very hostile to protect,
03:00to kind of already select the best sperms,
03:04and then they have to travel, adapt to a new environment, and find the egg.
03:09So that's by itself very fascinating, isn't it?
03:14A study she published in 2019 drew nationwide attention.
03:20Nearly 3,000 young men participated,
03:23felling out detailed questionnaires and submitting sperm samples.
03:27The results were disquieting,
03:30inspiring headlines like terrible sperm quality among Swiss recruits.
03:35One in six Swiss men is practically infertile.
03:38Maybe in 100 years we won't need men anymore.
03:42Broadcasters also sounded the alarm.
03:45According to Rabban's study,
03:47just one in three Swiss men has optimal semen quality.
03:51That means it meets all the WHO's threshold standards.
03:55Having suboptimal semen quality doesn't automatically mean infertility,
04:01but it does reveal a lot about a man's general health.
04:05Many factors influence sperm quality,
04:09among them smoking, alcohol, obesity,
04:13and high exposure to mobile phone radiation.
04:17Genetics and environment also play crucial roles.
04:22The geography is really a mirror of the environment.
04:26Of course, a person living in Geneva is not exposed to the same things
04:31a person living on a farm land is exposed to.
04:36Rabban and a research team at the Swiss Federal Institute of Technology in Lausanne
04:41have developed a new analytical method that shows for the first time
04:45that sperm quality is not evenly distributed across the country.
04:50There are regional differences called clusters.
04:53One negative cluster lies between Bern and Thun, marked here in red.
04:58A group of men there has comparatively low sperm quality.
05:04Another cluster, marked here in white, is positive.
05:08Men there have comparatively higher sperm quality.
05:12We were very curious.
05:14This is one of the first things we thought.
05:16Why are those clusters there?
05:20So what's the difference between these two regions?
05:25Rabban and her team compared their results with land use patterns.
05:30In the positive cluster, agricultural activity accounts for 28.3% of land use.
05:38In the negative cluster, it's 52%.
05:46Where we found the most significant results was in fodder and field crops.
05:50So most of the men who were in the cold spot
05:54were surrounded by a high percentage of fodder and field crops.
05:58Not by vineyards and not by forests.
06:01The research team published their findings in late 2025
06:06in an internationally renowned journal.
06:09So even though our cohort is nationwide and we're very happy about this,
06:16but we only somehow have 3,000 men.
06:19When we want to address and use these geographical methods,
06:23we actually need much more men to validate these clusters
06:28and validate the link that we made with the agriculture surfaces.
06:33Ellen Fritsche heads the Swiss Center for Applied Human Toxicology in Basel.
06:39For assessment of the findings, we need further research.
06:43But the approach, she thinks, is a good first step.
06:46Most importantly, it links sperm quality to regional factors.
06:54That's new and very innovative.
06:56Because it's showing us where in Switzerland
06:59potential sperm quality problems might be cropping up.
07:04In other words, people living in or near agricultural areas
07:08are exposed to different contaminants than people who live in cities.
07:13The study is a good start.
07:16But more detailed ones are necessary to confirm exact causes.
07:21We need more funding.
07:23Our field, the reproductive health field,
07:27is one of the most underfunded fields in biomedical sciences.
07:32So in conclusion, although there are new indications
07:36that sperm quality is a public health issue in Switzerland,
07:40funding for research is lacking.
07:44Like most men who struggle with the issue,
07:48Florian Schisser has never learned why his sperm is affected.
07:54When asked if it would have helped to know the cause,
07:57he says, he thinks it's good.
08:00Or at least to have an indication.
08:05Because you can't just keep hoping.
08:08That'll destroy you.
08:10At some point, you have to say, that's just the way things are.
08:14Then accept it and move on.
08:23We're not the only ones.
08:26Dolphins are also having problems reproducing.
08:29Changing environmental conditions like warmer waters and fewer fish
08:33may be the blame.
08:36Things are also changing in Shark Bay,
08:38a huge natural paradise on Australia's west coast,
08:42and home to one of the world's largest dolphin populations.
08:45Then being crazy to be younger,
08:48these changes better than males.
08:50Which raises the question,
08:51how do you actually determine a dolphin's sense?
08:57For over 40 years,
08:59researchers from the University of Zurich
09:01have been studying the behavior of dolphins
09:04in Shark Bay in Western Australia.
09:08They've shown that climate warming
09:11negatively affects fertility, birth rates,
09:14and survival rates in the bay's dolphins.
09:17New data could now provide more insights.
09:20With environmental conditions changing,
09:23are some dolphins adapting better?
09:25Males better than females?
09:27Or vice versa?
09:28Knowing each dolphin's sex is crucial
09:31if you want to answer questions like these.
09:35Today, Svenja Marfort is determining the sex of a dolphin in the California.
09:40First, we have to put our protective clothing
09:44because we don't want to contaminate the samples
09:46or mix our DNA with the dolphin DNA.
09:51Let's head into the extraction lab.
09:58These are the samples we collected on the boat.
10:02They traveled with us from Australia to Switzerland.
10:05They came from Australia to Switzerland.
10:08It's beautiful.
10:10Tissue samples are hard to come by in dolphin research.
10:14Svenja collected this batch in Shark Bay
10:16with a special air rifle designed specifically for taking biopsies.
10:34She's the only one on board allowed to shoot the darts that harvests the biopsy.
10:40And she only fires when the distance is perfect.
10:43Ensuring a clean hit.
10:45Good work.
10:47Nice.
10:48Waypoint taken.
10:51I love it.
10:56Very nice.
10:58With this small piece of fat and fat,
11:00you can do a whole lot of things with a small piece of fat and skin.
11:04You can do a whole lot of things with a small piece of fat and skin.
11:05Genetically, you can analyze kinship relationships across populations.
11:09For me, it's important to see whether they have specific genes that help them cope with their environment here.
11:17The high salinity, the rising water temperatures caused by climate change.
11:22To see whether there are genes that help them adjust to their changing environment.
11:29With such a tiny piece of skin and fat, but for us it holds endless potential.
11:34That's why it's so cool and so important that we can do this.
11:41Svenja Marfort had to complete a stringent training program to get a shooting license.
11:46Is anyone else a target?
11:47She always emphasizes treating the animals with the utmost caution and respect.
11:53Wow!
11:54Nice!
11:55Woohoo!
12:00I think he was a bit surprised.
12:03He wanted to check out the boat and usually nothing happens from the boat.
12:10This time something did and he felt something.
12:14It seems like it must be serious because it's a gun, but it only causes a little pinch.
12:20He's a dolphin that jumps around anyway, so we weren't surprised.
12:25He's a dolphin that jumps around anyway, so we weren't surprised.
12:30He already has a fin with a chunk missing, and has shark bites along his side.
12:38Really large wounds that have healed.
12:41Really large wounds that have healed.
12:43So that tiny little biopsy hole doesn't bother him at all.
12:55That tiny little biopsy hole doesn't bother him at all.
13:03A genetic analysis has revealed that Shark Bay's dolphin population has been there for at least 12,000 years.
13:11That basic knowledge provides a foundation for studying how the dolphins are adapting.
13:18For example, how the population is coping with changing environmental conditions.
13:23Dolphins like Fornia.
13:27During filming, the researchers didn't even know whether Fornia was male or female.
13:34That information has to wait for Zurich and the extraction lab at the university there.
13:40A little tissue from the biopsy is enough.
13:43You just need a tiny piece of skin to make a DNA analysis.
13:48Svenja says you really don't need much to extract DNA from it and takes the sample to the centrifuge.
13:54The next step is to break open the nuclei and cells to extract the DNA.
14:00You need those strands of the long molecule to pin down whether Fornia is a he or a she.
14:07One tiny piece in a giant puzzle.
14:11Back at Shark Bay.
14:14The researchers from the University of Zurich here not only collect DNA samples,
14:19they also observe the dolphin's social and mating behavior.
14:24Each animal is named and has its own data sheet where all observations are logged.
14:30Yeah, that's definitely a nice one.
14:31Fornia is nowhere to be seen today.
14:34But a group of other young dolphins is in the area.
14:39Shark Bay is home to the largest seagrass meadow in the world.
14:43Many fish species live in and around patches of it on the seabed,
14:48a good hunting ground for dolphins and other predators.
14:52But a massive marine heat wave in 2011 revealed just how vulnerable this ecosystem is.
14:59After water temperatures rose by up to 4 degrees Celsius in a very short time,
15:05over a third of the seagrass here died.
15:08That had dramatic consequences for the dolphins in Shark Bay.
15:13And biodiversity in general was hit hard.
15:25But what does that mean in concrete terms?
15:28How do we know the extreme weather event of 2011 affected the Shark Bay dolphins?
15:34The researchers from the University of Zurich now have both data and evidence.
15:40So here we have this green areas before the heat wave.
15:44This red area is the heat wave year and the years kind of after it.
15:51Or immediately after.
15:52And then the blue is sort of the time after.
15:55And then we've got here females in orange and the males in green.
16:01What's interesting, we see a bit of a different pattern between the two.
16:04Two sexes.
16:05So females seem to be okay during the heat wave.
16:10But afterwards in the years they really dropped.
16:14And then they were sort of able to recover a bit more.
16:16Whereas for the males they struggled in the heat wave.
16:18And they kind of continued to decline in survival.
16:21We can then also look.
16:22So especially for the males, the heat wave impact is here until today, right?
16:30Yeah, it seems like, well at least until a couple of years ago.
16:34Watch the data here.
16:35It hasn't really recovered back to the problem.
16:38That's why it is also important to know what sex Fournia is having.
16:43Yes, this will be important.
16:45Because to be included into my data set and be part of this analysis I need to know, particularly
16:52yes, what sex an animal is.
16:54So we can kind of include it as another really useful data point.
16:57And the more data points we have, the more accurate these models get.
17:01So when we get this data from Fournia, it means it's another animal that can be included into these models.
17:07One final step and we'll be able to say whether our dolphin is a male or a female.
17:14Und jetzt lade ich hier gerade Fournia auf das Gel.
17:19The test doesn't take long.
17:21Dann wissen wir hoffentlich gleich mehr.
17:24Here we go.
17:24Wir wären ready.
17:25The results are in.
17:26Ihr könnt schauen.
17:27Uh.
17:28The test is complete.
17:30Also, du hast ein Resultat?
17:33Ja.
17:33Nein, das schauen wir jetzt zusammen.
17:35Ich habe das Gel noch nicht in der Maschine.
17:38Aha.
17:39The gel has the answer to the question on everyone's mind.
17:49Who was right?
17:52Or is it a boy?
17:54It's a boy.
17:55It's a boy.
17:57Beide recht kam.
17:58You were right, both.
18:00So Fournia is a hymn.
18:00But many questions remain about the future of these fascinating animals.
18:05Their habitat is changing rapidly.
18:08But thanks to the research team, we now know a little more about the effects that's having on the dolphins
18:15of Shark Bay.
18:20Changing environmental conditions are also affecting our crops.
18:24Take rice for example.
18:26It grows best in shallow water.
18:28That's an advantage because most other plants don't flourish in flooded fields.
18:33So rice faces little competition.
18:36On the other hand, a rice plant's delicate weeds are highly sensitive to air pollutants like ozone.
18:43Which is why researchers in Germany are now working to breed a high-yield variety that's more resistant to the
18:50gas.
18:56The rice is an essential source of nutrition in many poorer countries, like densely populated Bangladesh, which has only around
19:12half the land area of Germany, but twice the population.
19:16The Bangladeshi economy is booming, and with it, the use of fossil fuels.
19:23So the air quality there is quite poor.
19:26Pollutants like nitrogen oxides are being emitted.
19:30And at high temperatures and strong sunlight, they react to fall ozone.
19:35A gas that damages rice plants and has a serious impact on harvests.
19:40Breeding ozone-resistant rice.
19:43That's the focus of Michael Frey's research at the University of Gießen.
19:47He's been contributing to global food security with his work on the topic for seven years now.
19:52In Bangladesh, ozone lowers yields by an estimated five percent.
19:59That's at least two million tons of rice lost every year in Bangladesh alone due to ozone damage.
20:06And our hope is to make a substantial contribution to reduce their toxins.
20:13A healthy rice plant is a lush green color.
20:17Photosynthesis works well.
20:19It produces lots of leaves and grains.
20:22Ozone-damaged leaves in comparison are spotted, which affects growth and yield.
20:28By crossing different strains, Frey's goal is to breed a variety of rice that's not affected by the gas.
20:36There's a variety that grows well in Bangladesh and gives good yields, but isn't ozone-tolerant.
20:44Then there's another variety that is tolerant, but it's not popular.
20:50Maybe because it grows too tall and falls too easily.
20:53So I'm trying to introduce the single trait, stress tolerance, into the modern local variety.
21:01The plants that emerge from this targeted crossing are exposed artificially to stress, large amounts of ozone.
21:10The university's greenhouses are perfect for this kind of research.
21:16By doing the working greenhouses, you can grow several generations per year, three to four.
21:24That saves time and is much faster than working in the field.
21:29Promising candidates are tested under real conditions in rice fields in Bangladesh.
21:35But why there?
21:36I went to Bangladesh for the first time as a B&HC candidate and got to know the country.
21:43They're very kind people, but there are also a lot of them, and they all need to be fed.
21:50We hope that people in Bangladesh will benefit from the rice variety's bread here in Gießen
21:57and that a lot of farmers there will choose to grow them.
22:00A success story at the University of Gießen that could one day make important contributions to food security in Bangladesh.
22:14As far as we know, life has only ever appeared here on Earth.
22:20But what if one day we discover intelligent life somewhere else?
22:27And how likely is that really?
22:31A viewer from Montenegro wants to know more.
22:35Will we one day find intelligent life beyond our planet?
22:41Although we've been searching for decades, we've never found convincing evidence of extraterrestrial neighbors in our galaxy, the Milky Way.
22:49No signals clearly made by other advanced civilizations.
22:56But there's a famous formula for calculating how many might be out there.
23:01Drake's equation is named after the researcher who came up with it in 1961.
23:08Theoretically, it could give us the number of civilizations in the Milky Way advanced enough to broadcast signals we can
23:16detect.
23:16In it, seven variables play roles.
23:20Let's take a look.
23:23First, we need the rate at which stars develop.
23:26We can estimate that.
23:28On average, fewer than 10 new stars form every year in our Milky Way.
23:35Second, we need the fraction of those stars that end up having planetary systems, like ours does.
23:41New observations indicate lots of them do.
23:46And then we need the number of planets with the right environment in those systems.
23:52Planets in the star's habitable zone.
23:55According to estimates, only about 20% have at least one planet temperate enough for liquid water, an important ingredient
24:03for supporting life as we know it.
24:06Then things get trickier.
24:08There's no data on the next variables, we just have to guess.
24:14Of those potentially habitable planets, we need the fraction where life actually appears.
24:21And then the fraction where these life forms would evolve intelligence.
24:25And it doesn't stop there.
24:27Next, we would need the fraction of those intelligent life forms that communicate using signals that we can actually detect.
24:37Finally, there's the time factor.
24:40How long a theoretical civilization broadcasts such signals.
24:45They can only move at the speed of light, and the Milky Way is really big.
24:49So the timing would also have to be just right for us to detect them.
24:55Because the Drake equation includes so many variables where we just have to guess,
25:00it's more of a thought experiment than a real tool for calculation.
25:06Depending on how positive you feel about the chances of intelligent aliens when plugging in the numbers,
25:13it can predict thousands of civilizations, or just the one we know about.
25:18Here on Earth.
25:21What are stars made of?
25:23How many colors can butterflies see?
25:26Could robots have these one day?
25:29Do you have a science question?
25:31Then send it to us as a video, text, or voice message.
25:35If we answer it in the show, then we'll send you a little gift as a thank you.
25:39So go on, just ask.
25:47That wraps things up for now.
25:50We hope you enjoyed the show, and we look forward to seeing you next time on Tomorrow Today.
25:56Bye-bye!
26:09Bye-bye!
26:09Bye-bye!
26:10Bye-bye!
26:10Bye-bye!
26:10Bye-bye!
26:10Bye-bye!
26:11Bye-bye!
26:11Bye-bye!
Comments