Scientists discovered why animals lost the ability to make nine out of eighteen amino acids they need to survive. Instead of making these “essential” amino acids themselves, animals now get them from food. Researchers found that making these amino acids takes a lot of energy, especially for animals that need lots of oxygen to survive. By outsourcing this job to their diet, early animals could save energy and use it for other important functions. This discovery helps explain how animals evolved and why we need to eat foods with complete proteins.
The Quick Take
- What they studied: Why animals stopped making nine amino acids (building blocks of proteins) and started getting them from food instead
- Who participated: This was a computational study analyzing genes from many different animals and their single-celled relatives, not a study with human participants
- Key finding: Making essential amino acids costs animals a lot of energy. When animals evolved to rely on food for these amino acids instead, they could save that energy for other uses, which gave them an advantage in survival and growth
- What it means for you: This explains why humans and other animals need to eat foods with complete proteins—our bodies literally cannot make nine amino acids on our own. Eating a variety of protein sources helps ensure you get all the amino acids your body needs
The Research Details
Scientists used computer analysis to study the genes of many different animals and compared them to single-celled organisms. They looked at which amino acids are expensive to make (require lots of energy) and which ones are cheap. The researchers then used statistical tests to see if there was a pattern: did animals lose the genes to make the expensive amino acids? They also examined how often different amino acids appear in animal proteins compared to single-celled organisms.
This type of study is called a phylogenomic analysis, which means scientists looked at genes across the evolutionary family tree of life. Instead of doing experiments in a lab, they analyzed existing genetic information to understand how and why animals evolved the way they did.
The key insight was comparing energy costs: making some amino acids requires much more energy than making others, especially when organisms need lots of oxygen (which is true for most animals). The researchers tested whether this energy cost explained why animals gave up making certain amino acids.
Understanding why animals evolved this way helps us understand how life works. It shows that evolution isn’t random—animals made specific changes that helped them survive better. This research also explains why nutrition matters: because animals can’t make these nine amino acids, we absolutely must get them from food. This knowledge helps nutritionists and doctors understand what foods humans need to stay healthy.
This study was published in Nature Communications, a highly respected scientific journal. The research used advanced computational methods and statistical tests designed to detect evolutionary patterns. The scientists compared their findings across many different animal species, which strengthens their conclusions. However, because this is a computational study analyzing genes rather than a direct experiment, the findings are based on patterns in data rather than controlled testing. The results suggest a strong explanation for why animals evolved this way, but scientists may continue to refine this understanding with future research.
What the Results Show
The main discovery is that the nine amino acids animals cannot make are significantly more expensive to produce than the nine amino acids animals can still make. This energy cost is especially high for animals because they live in oxygen-rich environments and have high energy demands. Using statistical tests, researchers found strong evidence that this energy cost is the reason animals lost the genes to make these amino acids over millions of years of evolution.
The researchers also found something surprising: modern animals use these expensive amino acids more frequently in their proteins than their single-celled relatives do. This suggests that once animals outsourced the production of these amino acids to their diet, they became free to use them more liberally in their proteins without worrying about the energy cost of making them. It’s like once you can buy something instead of making it yourself, you’re more willing to use it.
The study shows that this wasn’t a random accident of evolution. Instead, it appears to be a smart adaptation: animals made a trade-off where they gave up the ability to make expensive amino acids in exchange for saving energy that could be used for growth, movement, and reproduction. This energy savings likely gave early animals a significant advantage over their competitors.
The research also revealed that this change happened at a specific point in evolutionary history—right at the origin of animals. This means that as single-celled organisms evolved into the first animals, they underwent this metabolic change. The timing is important because it suggests this wasn’t a gradual change but rather a fundamental shift in how animals work. Additionally, the study found that different types of animals show similar patterns, suggesting this was a universal change across all animal life rather than something that happened in just one group.
Previous research had already discovered that animals can’t make nine amino acids, but scientists didn’t fully understand why this happened. Some researchers thought it might be due to random genetic changes or accidents. This new study provides a much more satisfying explanation: it happened because of energy efficiency. The research supports the idea that evolution is shaped by practical advantages, not just random chance. This fits with modern evolutionary biology, which shows that organisms tend to evolve traits that help them survive and reproduce better.
This study analyzed genes and proteins using computer models rather than conducting direct experiments, so the conclusions are based on patterns in data rather than controlled testing. The researchers couldn’t directly measure the energy cost of making amino acids in ancient animals, so they had to estimate based on modern organisms. Additionally, while the statistical evidence is strong, it’s possible that other factors also played a role in why animals lost these genes. The study focuses on the origin of animals but doesn’t fully explain why some animals later regained the ability to make certain amino acids. Finally, this research is quite new and will likely be refined as other scientists test and build upon these findings.
The Bottom Line
For general health, ensure your diet includes complete proteins that contain all nine essential amino acids. Good sources include meat, fish, eggs, dairy, beans combined with grains, nuts, and seeds. If you follow a vegetarian or vegan diet, eat a variety of plant proteins throughout the day to get all essential amino acids. This research provides scientific backing for why balanced nutrition matters—your body literally cannot function without these nine amino acids from food. Confidence level: Very high, based on well-established nutritional science.
Everyone should care about this research because all humans need these nine amino acids to survive. This is especially important for growing children and teenagers, pregnant women, athletes, and people recovering from illness—all of whom have higher protein needs. People following restrictive diets should pay extra attention to ensure they’re getting all essential amino acids. This research doesn’t change recommendations for people with specific medical conditions, who should continue following their doctor’s advice.
You won’t notice immediate changes from understanding this research, but eating adequate complete proteins every day supports your body’s ability to build and repair muscles, make enzymes, and maintain overall health. The benefits accumulate over time—weeks and months of proper nutrition lead to better energy, stronger muscles, and improved overall health.
Want to Apply This Research?
- Track daily protein intake by logging all protein sources consumed (meat, fish, eggs, dairy, legumes, nuts, seeds) and note whether you’re eating complete proteins or combining incomplete proteins. Aim to track whether you’re hitting your daily protein target based on your age, weight, and activity level.
- Set a daily reminder to include at least one complete protein source at each meal, or if eating plant-based proteins, ensure you’re combining different types throughout the day (like beans with rice). Use the app to log these choices and see patterns in your protein variety over time.
- Weekly review of protein sources consumed to ensure variety and completeness. Track energy levels and recovery from exercise as potential indicators of adequate amino acid intake. Monitor this over 4-8 weeks to see if more consistent complete protein intake correlates with improved energy and performance.
This research explains the evolutionary origin of why animals need dietary amino acids but does not constitute medical or nutritional advice. Individual nutritional needs vary based on age, sex, activity level, health status, and medical conditions. People with specific health concerns, dietary restrictions, or medical conditions should consult with a registered dietitian or healthcare provider before making significant changes to their diet. This article is for educational purposes and should not replace professional medical or nutritional guidance.