Before Jonas Salk and his team invented a vaccine for the polio virus in 1952, humans had battled its paralyzing effects for a millennia. But a 30-year endeavor to rid the world of the incurable disease will render it virtually extinct by the end of 2017. This monumental achievement, rivaled only by the eradication of smallpox in 1980, is the result of coordinated efforts by scientists and volunteers to track its spread and deliver vaccines both orally and by injection to billions around the world.
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It’s never too late to learn a language – adults and kids bring different strengths to the task
Age matters, but it never closes the door.
There’s a common assumption that if someone starts learning a language when they are very young, they will quickly become fluent.
Many people also assume that it will become much harder to learn a language if they start later in life.
Research into language learning shows that how old someone is when they learn a language does matter, but there is no point at which the ability to learn a language switches off.
While a young language learner can more easily acquire a native accent, adults retain the ability to learn new languages well into later life. Anyone can continue to learn and refine their vocabulary and grammar. Other factors, like motivation, can also play a role for learners of all ages.
I am a linguist and the author of a forthcoming book, “Beyond Words: How We Learn, Use, and Lose Language,” which looks at how language is learned, used and lost across a lifespan — and why age alone does not set hard limits on our linguistic abilities.
Instead, the strategies learners use, the outcomes they achieve most easily, and how others judge their progress can all change over time.
How age shapes language learning
Someone’s age can influence their language learning ability in a variety of ways.
Scientists sometimes talk about sensitive periods, or an early development window in which the brain is especially receptive to certain kinds of input.
When it comes to language, babies and children are particularly sensitive to the sound patterns of speech. They can also pick up on subtle phonetic distinctions that adults struggle to perceive or reproduce.
This helps explain why children who grow up bilingual often sound native in both languages. Accents, more than vocabulary or grammar, are where age-related differences are most pronounced.
Sensitive periods are found in other animals, too, especially birds, which have an early sensitive period for learning their species-specific song from an adult tutor.
After this window closes, learning a new language is still very much possible. But it usually takes more conscious effort and practice.
Studies also show that children exposed to a second language early, roughly before puberty, are more likely to develop nativelike pronunciation and intonation.
Brain imaging research shows that people who learn two languages early in life tend to process both languages in the same parts of the brain. Those who learn a second language later often use slightly different brain areas for each language.
In practical terms, early bilinguals are more likely to switch between languages effortlessly. Later learners may have to more consciously work through their second language, especially at first.

Second grade students do classwork during a Spanish-only, dual immersion class in University Hill Elementary School in Boulder, Colo., in 2022. Glenn Asakawa/The Denver Post via Getty Images Benefits to learning a language as an adult
Pronunciation is only one part of language proficiency. Adults bring their own strengths to the task.
Unlike young children, adult learners already have a fully developed first language. They also have skills in reasoning and pattern recognition, as well as an awareness of how language works.
This allows adults to learn in a more deliberate way, as they study grammar rules and consciously compare languages. Adults are also more likely to rely on deliberate strategies, such as memorization, to learn a language.
In classroom settings, adults often outperform children in early stages of learning, particularly in reading and writing.
Language learning never truly stops. Even in adulthood, people continue to develop and refine their first language, shaped by their education, work and social environment, and how they use it day to day.
While it may be harder for adults to acquire a nativelike accent later in life, the good news is that grammar, vocabulary and fluency remain well within reach for most adult learners.
Benefits of learning a language as a kid
Children, meanwhile, tend to learn languages implicitly, through immersion and interaction, often without conscious attention to rules.
Social and emotional factors also play a major role in successfully learning a language.
Children are generally less self-conscious than adults and more willing to take risks when speaking.
Adults, by contrast, are often acutely aware of mistakes and may hesitate to speak for fear of sounding foolish or being judged.
Research consistently shows that being willing to communicate is a strong predictor of success in learning a new language. Anxiety, inhibition and negative feedback from others can significantly slow progress, regardless of age.
Accent, bias and social pressure
Other factors, like social pressure and discrimination, matter as someone tries to learn a new language.
Research into language and identity shows that listeners frequently associate accented speech with lower intelligence or competence, despite there being no connection between accent and cognitive ability.
Non-native speakers often experience stigmatization, discrimination and prejudice from native speakers.
This bias can discourage adult learners and reinforce the false belief that successful language learning means sounding native.
Motivation and aptitude matter, too
Motivation is another key factor that affects learners of all ages.
People learn new languages for many reasons: a new country, work, school, relationships or interest in another culture.
Research distinguishes between the different reasons people learn a language. Some are practical, like advancing a career or passing a test. Others are personal, such as wanting to connect with a community, culture or family.
Learners who feel a strong personal or emotional connection to the language are more likely to keep going even when it gets difficult, and they often reach higher levels of fluency than those without this connection.
Other people have a natural aptitude for learning a language and can pick it up easily. Perhaps they quickly notice sound patterns, or they can remember new vocabulary after hearing it once or twice.
Language aptitude is different from intelligence and varies from person to person. Aptitude makes success in learning a language more likely, but it doesn’t guarantee it.
Learners with average aptitude can still become very proficient in new languages as adults if they have consistent exposure, practice and motivation.
Different ages, different strengths
So is it better to learn a second language as a child or as an adult? Research suggests the more useful question is which aspects of language learning, such as pronunciation, fluency or long-term mastery, matter most.
Learning a new language early makes it easier to sound like a native speaker and to use the language smoothly, without having to think about the rules.
Learning that language later in life draws on adult strengths, such as planning, problem-solving and focused practice.
Ultimately, some people pick up languages quickly while others struggle, regardless of how old they are.
Beliefs about language learning shape education policy, parenting choices and how multilingual speakers are treated in everyday life.
When adults are told they’ve missed their chance to learn a language, many never bother to try. When foreign accents are treated as flaws, capable speakers can be unfairly discriminated against.
In fact, research shows that learning a language is possible at any age – it’s a lifelong, achievable journey, rather than a race against the clock.
This article originally appeared on The Conversation. You can read it here.
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What does the appendix do? Biologists explain the complicated evolution of this inconvenient organ
It may be inconvenient, but the appendix is no evolutionary mistake.
Most people know only two things about the appendix: You don’t need it – and if it bursts, you need surgery fast.
That basic story traces back at least to Charles Darwin, the English naturalist who developed the theory of natural selection. In “The Descent of Man,” he described the appendix as a vestige: a leftover from plant-eating ancestors with larger digestive organs. For more than a century, that interpretation shaped both textbook and casual medical wisdom.
But the evolutionary story of the appendix turns out to be much more complicated.
Along with our colleague Helene M. Hartman, a student preparing for a career in health care, we combined our expertise in behavioral ecology, biology and history to review the scientific literature on the appendix, expecting a simple answer.
Instead, we found an organ that evolution kept reinventing, more interesting than most people imagine.
How did the appendix evolve?
The appendix is a small pouch branching off the first section of the large intestine. Its shape and structure vary widely across species – a clue that evolution may have tinkered with it more than once.
Some species, including certain primates such as humans and great apes, have a long, cylindrical appendix. In others, including several marsupials such as wombats and koalas, the appendix appears shorter or more funnel-shaped. Still others, including some rodents and rabbits, have differently proportioned or branching structures. This structural diversity suggests that evolution has modified the organ under different ecological conditions.

The appendix can be oriented in the body in multiple ways. Mikael Häggström, M.D./Wikimedia Commons That suspicion is supported by evolutionary analyses. Comparative studies show that an appendix-like structure evolved independently in at least three distinct lineages of mammals – marsupials, primates and glires, a group that includes rodents and rabbits. A broader evolutionary survey found that the appendix evolved separately at least 32 times across 361 mammalian species.
When a trait evolves repeatedly and independently, biologists call this convergent evolution. Convergence does not mean a structure is indispensable. But it does suggest that, under certain environmental conditions, having that structure provided a consistent enough advantage for evolution to favor it again and again.
In other words, the appendix is unlikely to be a useless evolutionary accident.
What does the appendix do?
The appendix supports the immune system. It contains gut-associated lymphoid tissue – immune cells embedded in the intestinal wall that help monitor microbial activity in the gut. In early life, this tissue exposes developing immune cells to intestinal microbes, helping the body learn to distinguish between harmless symbionts and harmful pathogens.
The appendix is particularly rich in structures called lymphoid follicles during childhood and adolescence, when the immune system is still maturing. These immune components participate in mucosal immunity, which helps regulate microbial populations along the intestinal lining and other mucosal surfaces. Lymphoid follicles produce antibodies, such as immunoglobulin A, to neutralize pathogens.
Researchers have also proposed that the appendix acts as a microbial refuge. Some have suggested that biofilms – thin, structured communities of bacteria – line the appendix. During severe gastrointestinal infections that flush much of the gut microbiome from the colon, beneficial bacteria sheltered within these biofilms may survive and help repopulate the intestine afterward. Those beneficial microbes assist with digestion, compete with pathogens and interact with the immune system in ways that reduce inflammation and promote recovery.
These hypotheses motivated a question our team explored: If the appendix helps preserve microbial stability, could removing it subtly affect reproductive fitness?
Older clinical concerns suggested that appendicitis or appendectomy might impair fertility by causing inflammation and scarring – known as tubal adhesions – in the fallopian tubes. Such scarring could physically obstruct the egg’s passage to the uterus. But several large studies have since found no decrease in fertility after appendectomy – in some cases, researchers found a small increase in pregnancy rates.
The appendix appears to have multiple functions, including immune and microbial ones. Affecting fertility, however, does not seem to be one of them.
Evolutionary importance and modern life
While the appendix has an interesting past, with evolution continually reinventing it, its modern importance is modest at best. Darwin underestimated the organ’s history, but his instinct wasn’t far off in the medical present: Some parts of human biology mattered more in the environments people evolved in than in the lives they lead today.
Early humans lived in environments with little sanitation and strong social contact – perfect conditions for outbreaks of pathogens that cause diarrhea. An appendix that quickly restored the microbiome after infection could significantly improve survival. But over the past century, clean water, improved sanitation and antibiotics have sharply reduced deaths from diarrheal diseases in high-income countries.
As a result, the evolutionary pressures that once favored the appendix have largely disappeared. Meanwhile, the medical risks of keeping the appendix – most notably appendicitis – remain. Modern surgery typically treats an infected appendix by removing it. A structure that was once a global evolutionary advantage is now more of a medical liability.
This mismatch between past adaptations and present environments illustrates a core principle in evolutionary medicine: Evolution optimizes for survival and reproduction in ancestral environments, not for health, comfort or longevity in modern ones.
Evolution operates at the level of populations over generations, favoring traits that increase average reproductive success, even if those traits sometimes harm individuals. Medicine works the other way around – helping individuals thrive in the present world rather than survive the past one.
The appendix is not an IKEA spare part included “just in case,” but neither is it essential today. Human biology has many traits that were once beneficial, now marginal – and understanding them allows medicine to make better modern decisions.
This article originally appeared on The Conversation. You can read it here.
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