Which came first, the chicken or the egg? We have the answer! ｜ Expo Daily

Which came first, the chicken or the egg?

Nature: “The egg came first!”

Chromosphaera perkinsii is an organism discovered in Hawaii in 2017. The earliest signs of its existence on Earth date back more than a billion years, long before the emergence of the first animals. Although it is a single-celled species, it can also aggregate into multicellular forms to live together. A research team from the University of Geneva in Switzerland observed that the multicellular structure of this species has a striking similarity to animal embryos. Signs suggest that the mechanism responsible for embryonic development existed in single-celled organisms long before the emergence of multicellular animals.

Before this, people have always had this doubt: multicellular organisms always come from embryos, and embryos always come from multicellular organisms . This is a question similar to whether the chicken or the egg came first.

The species Chromosphaera perkinsii diverged from the animal evolutionary line more than a billion years ago, providing valuable insights into the mechanisms that may have led to the transition to multicellularity.

The scientists found that once the organism reaches its maximum size, it divides without growing further, forming multicellular colonies similar to the early stages of animal embryonic development.

Surprisingly, the way these cells divide and the three-dimensional structures they adopt are strikingly similar to the stages of animal cell growth. For example, they also grow certain specialized regulatory cells that regulate the growth of other cells by secreting hormone-like substances. This suggests that the genetic program that controls the generation of complex multicellularity existed long before the emergence of multicellular animals .

"It's amazing that a recently discovered species allows us to go back more than a billion years," explains Marine Olivetta, an author of the paper. In fact, this study shows that the principles of multicellular development existed before the emergence of animals .

That is, nature had the genetic tools to create eggs long before it invented chickens. So the answer to this question should be "the egg came first, then the chicken."

The discovery could also shed new light on many ancient fossils that resemble embryos, and could challenge some traditional ideas about multicellular biology.

The cells of this species show a polarity that is clearly similar to that of egg cells. Image credit: Dudin lab

References: Marine Olivetta, Chandni Bhickta, Nicolas Chiaruttini, John Burns, Omaya Dudin. A multicellular developmental program in a close animal relative. Nature, 2024; DOI: 10.1038/s41586-024-08115-3

Why do we sleep better when we turn off the lights?

And you feel like you’re falling asleep faster?

When talking about sleep, it is easy to associate it with melatonin. Melatonin is a hormone in the human body that can regulate sleep. It is a small molecule indoleamine substance essential for life. Melatonin in higher animals is produced by the pineal gland, then enters the blood to reach its receptors, playing an important role in sleep regulation.

Melatonin is also called the "dark signal" because melatonin is mainly secreted in the dark, with increased secretion at night and restricted secretion during the day. Once the environment becomes dark, melatonin begins to be secreted and acts on the neurons in the paraventricular nucleus of the thalamus (PVT), making it easier for the brain to enter a resting state.

When the lights are on, even if you close your eyes you can still feel the red light through your eyelids. At the same time, the shadows cast by the light on objects can easily affect your sleep and cause disturbance. It takes some time to adapt before you can fall asleep.

Image source: pixabay

The pine cone you picked up is not a fruit?

Pine cone is a general term for the spherical or oval cones of pine plants. However, although pine cones are called "fruits", they are not real fruits.

Pinaceae plants are gymnosperms, monoecious. The female reproductive organ is called megasporophylls, with ovules naked at the base of the megasporophylls (without carpels), and the male reproductive organ is called microsporophylls.

The microspore mother cells undergo meiosis to form pollen grains. When the pollen grains (male gametophyte) in the pollen sac complete the fertilization process with the archegonium (mature female gametophyte), the zygote develops into an embryo at the base of the megaspores. The embryo undergoes differentiation, and after maturity, the entire ovule develops into a seed, while the megaspores harden into woody seed scales, and the bracts develop into hard bract scales.

The "pine cone" we see is a layer of spirally interlocking and upwardly curved seed scales arranged in a tower shape, so the "pine cone" is also called a "pine cone". The seeds developed from the ovules hide at the base of the seed scales and escape when the cones crack and spread. Because the seeds are not covered by the pericarp and grow naked on the seed scales, gymnosperms get their name.

Because of the lack of pericarp, "pine cones" cannot be called true fruits, but rather a complex of seeds, seed scales, bract scales and cone axis (central axis).

Cone development process | Adapted from Wikipedia

Illustration: Gao Jie

Walk uphill and climb stairs,

Blood pressure is dropping

New research suggests that getting small amounts of vigorous activity each day, such as uphill walking or climbing stairs, may help lower blood pressure.

The research team analyzed the health data of 14,761 volunteers from five countries to understand the relationship between exercise behavior and blood pressure. Using statistical models to estimate the impact on blood pressure in each case, it was found that if sedentary behavior is replaced with 20-27 minutes of vigorous exercise every day, the incidence of cardiovascular disease in the population may be reduced by 28%.

The results of the study show that for most people, vigorous exercise is the key to lowering blood pressure, while less intense exercise such as walking does not have a significant effect on lowering blood pressure. The good news is that if your body is not suitable for long-term intense exercise, you can try even 5 minutes of intense exercise, which can have a significant effect on lowering blood pressure.

For those who don't exercise regularly, walking can still have some benefits on blood pressure. But if you want to change your blood pressure, increasing the workload on your cardiovascular system through exercise will have the greatest effect.

The research, published in the journal Circulation, was conducted by an international academic collaboration led by the University of Sydney, Australia, and University College London (UCL), UK.

Image source: pixabay

Choose one of more than 500 grass species to cross with wheat

In the 1950s, stripe rust, known as the "cancer" of wheat, occurred frequently. At that time, Li Zhensheng, who was only in his 20s at the Northwest Institute of Agricultural Biology of the Chinese Academy of Sciences, selected Elytium longissima from more than 500 forage grasses and conducted distant hybridization with wheat to improve wheat's disease resistance.