How the Human Microbiome Develops From Birth Through Aging

The human microbiome is not a single community that develops in one way. The gut, the mouth, the skin, and other body sites each host their own microbial ecosystem, and these ecosystems assemble and mature on different timelines. Colonization begins around birth, changes quickly through infancy and childhood, shifts again at puberty, settles into a relatively stable adult pattern, and continues to change into older age.

This guide follows that story across life. It focuses on time and development, how microbial communities at different body sites emerge and change, rather than repeating what the microbiome is. Early life is an influential window, and researchers link early differences to later health, but most of these findings are associations rather than proof of cause, and the microbiome stays modifiable.

Quick Answer: How does the human microbiome develop across life?

Major microbial colonization begins around birth and is shaped first by delivery mode, feeding, and environment. Development is rapid through infancy and childhood, and different body sites develop differently: the gut becomes Bifidobacterium-rich in breastfed infants and matures with weaning, while the skin and mouth follow their own paths. Development continues well beyond age three, and puberty brings further, sex-specific changes, most visibly in the skin. Adulthood is relatively stable but still responds to diet, medication, illness, and life transitions, and older age brings individualized changes rather than a single uniform decline. Early patterns may be associated with later health, but they do not predetermine it.

New to the topic? Start with our foundational guides:

What Is the Human Microbiome? A Complete Guide to Microbes, Immunity & Digestion
Oral Microbiota & Gut Health: How the Mouth Shapes the Entire Microbiome
The Gut–Brain Axis: How Microbes Influence Mood, Stress & Appetite

The Human Microbiome Is Not One Single Ecosystem

It helps to picture the body as a set of very different habitats. The gut is warm, largely oxygen-poor, and rich in food for microbes. The skin is cool, dry or oily depending on the site, and exposed to the outside world. The mouth has hard surfaces, saliva, and its own oxygen gradient. Each of these environments favors different microbes, so each develops its own community with its own timeline and its own strongest influences.

This is why the article treats development as site-specific. For a full account of gut development in particular, see our dedicated guide on how the gut microbiome forms and changes. Here the gut is one example among several, used to show how human microbial development differs across the body.

How the Human Microbiome Changes Across Life

Birth: The Beginning of Major Microbial Colonization

At birth, a newborn meets a wide range of microbes for the first time. A classic multi-site study found that a newborn's communities start out fairly similar across the skin, mouth, nose, and gut, and only differentiate into distinct site-specific ecosystems over the following weeks and months. The immediate colonizers reflect delivery mode: babies born vaginally tend to pick up communities resembling the mother's, while babies born by caesarean section pick up more skin-associated and environmental microbes at first.

Newer strain-tracking work adds an important correction. The durable early colonizers of the gut come mainly from the mother's gut, or fecal, strains rather than from vaginal microbes, which tend to be transient. Caesarean birth is associated with reduced transmission of some maternal gut strains and more environment-associated bacteria early on, and similar effects follow antibiotics given around birth or not being breastfed. These early differences tend to narrow over the first year or two. Delivery mode influences how colonization starts; it does not decide a child's health, and caesarean birth is often medically necessary.

Infancy: Ecosystems Begin to Take Shape

In infancy the gut is usually dominated by Bifidobacteria, which thrive on the human milk oligosaccharides (HMOs) in breast milk. It is worth being clear about diversity here: an infant gut is naturally low in diversity, and that is normal and age-appropriate, not a deficiency. A Bifidobacterium-rich community is what a healthy young infant gut tends to look like, and diversity increases later, with weaning.

Breastfeeding is a meaningful modifier of early development, not a permanent destiny, and formula-fed infants can also develop healthy microbiomes. Meanwhile the skin and mouth are starting to build their own communities, shaped by contact, environment, and feeding. Feeding choices are personal and often shaped by circumstances, and the honest message is about composition and trajectory, not a healthy-versus-unhealthy verdict.

Weaning and Early Childhood: A Major Ecological Transition

The move to solid foods, weaning, is one of the biggest turning points in development. As milk becomes a smaller part of the diet, fiber and a wider range of foods arrive, and the gut community shifts toward a more adult-like state. A study that followed twins from birth to eight years of age identified weaning as a critical inflection point that shaped which strains persisted into childhood, and a large early-childhood study describes roughly three phases: a developmental phase through the middle of the first year, a transitional phase driven by weaning, and a more stable phase by around age three. The mouth changes too, as teeth erupt and create new surfaces for microbes to colonize. For gut-specific detail, see our gut microbiome development guide.

Childhood: Expanding Diet, Environment, and Social Exposure

Through childhood, diet and environment continue to shape microbial communities across the body. Fiber intake, time in natural settings, contact with pets and other children, sleep, stress, dental development, and antibiotic history all leave a mark. Longitudinal studies that follow children to eight and even ten years of age show the microbiome keeps maturing well past infancy, with strains turning over and community patterns shifting. Higher microbial diversity in childhood is associated with favorable immune and metabolic patterns in some studies, but these are associations rather than proof that diversity by itself drives health, and there is no single ideal childhood microbiome.

Puberty and Adolescence: Hormonal and Environmental Changes

Adolescence is an active developmental stage, and it is where body-site differences become most visible. In the gut, longitudinal research shows the community continues to mature toward an adult-like profile during and after puberty, in a sex-specific way that tracks with sex hormones.

The skin shows the clearest change. Rising sex hormones increase sebum production, which favors lipophilic microbes: the bacterium Cutibacterium acnes and the yeast Malassezia become more prominent, in a pattern that differs between girls and boys and tracks with pubertal stage. The oral community also matures, and the urogenital tract shifts as well; after puberty, for example, the vaginal environment typically becomes Lactobacillus-dominant under the influence of estrogen. These are developmental transitions, not a microbiome "disruption," and diet, sleep, stress, and environment continue to influence them. For the mouth specifically, see our guide on how the oral microbiome shapes gut health.

Adulthood: Relative Stability With Continued Adaptability

By adulthood, microbial communities across the body are relatively stable, yet they remain responsive. A person tends to keep a fairly consistent core community at each site, while diet, medication, illness, alcohol, sleep, stress, and environment can shift the balance. The most consistent lever for the gut is dietary pattern over time, a varied, fiber-rich, plant-heavy diet, rather than any single supplement.

Adult Life Transitions

Certain physiological transitions can shift microbial ecosystems in adulthood, including pregnancy, menopause, significant illness, and courses of medication. These are worth noting as part of a lifespan view, though each is a large topic in its own right. Where you want to go deeper, follow the dedicated guides in this series rather than treating a single transition here.

Aging: Individualized, Not a Uniform Decline

Aging does not simply erase the microbiome. Newer research complicates the older idea that diversity and beneficial species uniformly fall. In large cohorts, healthy aging is associated with a gut microbiome that becomes more individualized with age and shows a gradual depletion of some common core genera, and this pattern predicted better survival in the oldest adults. Skin and oral communities also change with age. Inflammation, frailty, medication, and living environment all shape later-life patterns, so the picture is individualized rather than a single across-the-board decline. For how these ideas connect to healthy aging, see our overview of the gut and oral microbiome in longevity.

What the Evidence Suggests About Microbiome Development

What Science Knows and What Is Still Being Studied

Relatively well supported

• Major microbial colonization begins around birth, and early development is rapid.

• Different body sites develop along different timelines.

• Feeding influences the infant gut, and HMOs strongly interact with Bifidobacteria.

• Delivery mode affects early microbial composition, and antibiotics can alter developing communities.

• Weaning changes gut microbial ecology, and development continues through childhood and puberty.

Still uncertain

• What counts as an ideal microbiome for any given person.

• Whether individual early microbial patterns directly cause later disease, or travel alongside other factors.

• How permanent early microbial differences really are.

• Whether a specific probiotic creates durable, lifelong changes.

• Whether increasing one organism, such as Akkermansia, improves long-term health.

What Supports Healthy Microbial Development Across Life

Most of what supports microbial development at any age is ordinary and well established: where possible, breastfeeding in infancy; a varied, fiber-rich, plant-heavy diet as solid foods and later life continue; time outdoors and everyday environmental contact; adequate sleep; and using antibiotics when a clinician judges them necessary while avoiding unnecessary use. The goal is not to chase a perfect or maximally diverse microbiome, but to support an age-appropriate one and to keep healthy habits steady over time.

Key Takeaways

• The human microbiome is several ecosystems, not one, and they develop on different timelines.

• Colonization begins around birth; delivery mode and feeding shape the start but do not decide later health.

• Weaning is a major turning point, and development continues through childhood and puberty.

• The skin shows the clearest puberty-driven change, shifting toward lipophilic microbes.

• Aging is individualized, and the microbiome stays modifiable throughout life.

A Note on Supplements

Most of what supports a healthy microbiome is not a supplement. Akkermansia muciniphila is one of many organisms whose abundance changes across development and is studied in relation to mucus-associated microbial ecology, rather than a must-have for any age group. If you are an adult who wants to add a supplement to a healthy routine, you can learn more about our Akkermansia Chewable and about food-first ways to support Akkermansia. Products containing Akkermansia are intended for adults and adolescents aged 12 and over, and are not for infants or young children. For anything concerning an infant's or child's feeding, antibiotics, or health, speak with a pediatrician.

Common Questions About How the Microbiome Develops

1. When does the human microbiome begin developing?

Major colonization begins around birth, when the newborn is rapidly exposed to microbes from the mother and the environment. Communities across the body then develop quickly over the first years of life.

2. Does the microbiome develop the same way at every body site?

No. At birth, communities at different sites start out similar, then differentiate into distinct ecosystems. The gut, mouth, and skin each follow their own timeline and respond to different influences, which is why development is best understood site by site.

3. How does birth method (vaginal versus caesarean) influence development?

Delivery mode shapes the earliest colonizers. Durable gut strains come mainly from the mother's gut rather than from vaginal microbes, which tend to be transient. Caesarean birth is associated with some early differences that usually narrow over the first year or two, and it is often medically necessary. Delivery mode is one influence among many, not a verdict on a child's health.

4. How does breastfeeding shape the infant microbiome?

Breast milk contains HMOs (human milk oligosaccharides) that feed beneficial Bifidobacteria and support the developing gut. A low-diversity, Bifidobacterium-rich infant gut is normal and age-appropriate. Breastfeeding is a helpful modifier, not a permanent destiny, and formula-fed infants can also develop healthy microbiomes.

5. Why is weaning important?

Weaning, the move to solid foods, is one of the biggest turning points in development. It brings fiber and variety and pushes the gut community toward an adult-like state. A study following children to age eight identified weaning as a critical inflection point that shaped which strains persisted into childhood.

6. Do antibiotics permanently change a child's microbiome?

Antibiotics can reduce microbial diversity for a time, and some studies link repeated early use to later allergy or metabolic differences. The microbiome usually recovers, and necessary antibiotics should not be avoided when a clinician prescribes them. The sensible goal is to avoid unnecessary use, not to fear needed treatment.

7. Does the microbiome keep changing during puberty?

Yes. The gut continues maturing toward an adult profile in a sex-specific way, and the skin changes most visibly: rising sex hormones increase sebum and favor lipophilic microbes such as Cutibacterium and Malassezia. Oral and urogenital communities mature as well. These are developmental transitions, not a disruption.

8. Can the adult microbiome still change?

Yes. Although adult communities are relatively stable, they respond to diet and lifestyle, and to transitions such as illness, medication, pregnancy, and menopause. Fiber-rich, plant-varied eating, along with sleep, movement, and stress management, are the most consistent ways to support the gut.

9. How does aging affect microbial ecosystems?

Aging brings individualized changes rather than a single uniform decline. Large studies link healthy aging to a gut microbiome that becomes more unique to the person over time, alongside a gradual depletion of some common core genera. Health status, frailty, diet, and medication all shape later-life patterns.

Scientific References

1. Dominguez-Bello MG, Costello EK, Contreras M, et al.
   Delivery mode shapes the acquisition and structure of the initial microbiota across multiple body habitats in newborns
   PNAS 2010;107(26):11971-11975
   doi:10.1073/pnas.1002601107 (Human; multi-site newborn colonization)

2. Shao Y, Forster SC, Tsaliki E, et al.
   Stunted microbiota and opportunistic pathogen colonization in caesarean-section birth
   Nature 2019;574(7776):117-121
   doi:10.1038/s41586-019-1560-1 (Human cohort; delivery mode and maternal strain transmission)

3. Stewart CJ, Ajami NJ, O'Brien JL, et al.
   Temporal development of the gut microbiome in early childhood from the TEDDY study
   Nature 2018;562(7728):583-588 
   doi:10.1038/s41586-018-0617-x (Human longitudinal; early-childhood developmental phases)

4. Gut microbiome evolution from infancy to 8 years of age
   Nature Medicine 2025 
   doi:10.1038/s41591-025-03610-0 (Human twin cohort to age 8; weaning as a critical inflection point)

5. Korpela K, Kallio S, Salonen A, et al.
   Gut microbiota develop towards an adult profile in a sex-specific manner during puberty
   Scientific Reports. 2021 (Human longitudinal; puberty and sex-specific gut maturation)

6. Park J, Schwardt NH, Jo JH, et al.
   Shifts in the skin bacterial and fungal communities of healthy children transitioning through puberty
   Journal of Investigative Dermatology 2022 (Human longitudinal; skin microbiome maturation with pubertal stage)

7. Wilmanski T, Diener C, Rappaport N, et al.
   Gut microbiome pattern reflects healthy ageing and predicts survival in humans 
   Nature Metabolism 2021;3(2):274-286
   doi:10.1038/s42255-021-00348-0 (Human cohorts, over 9000 people; healthy-aging pattern)

8. Cani PD, Depommier C, Derrien M, Everard A, de Vos WM.
   Akkermansia muciniphila: paradigm for next-generation beneficial microorganisms 
   Nature Reviews Gastroenterology and Hepatology 2022;19(10):625-637
   doi:10.1038/s41575-022-00631-9 (Review)

Written by Ali Rıza Akın

Microbiome Scientist, Author & Founder of Next-Microbiome

Ali Rıza Akın is a microbiome scientist with nearly 30 years of experience in translational biotechnology, systems biology, and applied microbiome research, spanning discovery, preclinical development, and clinical-stage translation.

His work focuses on how microbial ecosystems interact with human physiology, including:

• Gut barrier function and intestinal permeability

• Mucus-associated microbiota (Akkermansia-related systems)

• Oral–gut microbiome axis

• Short-chain fatty acids (SCFAs) and metabolic signaling

• Circadian rhythm–microbiome interactions

• Clinical Research Contributions

He has contributed to multiple clinical-stage microbiome programs, supporting bacterial strain discovery, optimization, and formulation design across different therapeutic areas, including:

Active Ulcerative Colitis (Inflammatory Bowel Disease)

Hyperoxaluria (Oxalate Metabolism Disorder)

Microbiome-driven gut health and inflammatory conditions

These studies were part of broader clinical development programs evaluating microbiome-based approaches. His contributions focused on the early-stage scientific and translational pipeline, including strain discovery, functional optimization, and multi-strain formulation design.

Scientific Contributions:

Ali Rıza Akın is the discoverer of Christensenella californii, a bacterial species associated with microbiome diversity and metabolic health.

He is a contributing author to scientific publications and Bacterial Therapy of Cancer (Springer), and the author of Bakterin Kadar Yaşa: İçimizdeki Evren: Mikrobiyotamız.

Approach:

His work emphasizes evidence-based microbiome science, long-term safety, and a systems-based understanding of how microbes influence human health.

Review and Sources

This article is written and reviewed by a microbiome scientist and draws on the peer-reviewed studies listed in the References. It separates well-supported findings from associations and open questions, labels the type and strength of the evidence, and treats microbiome development as an influential but modifiable, site-specific process rather than a fixed destiny. It is reviewed periodically against current research.

Medical Disclaimer

This content is for educational and informational purposes only and is not medical advice, diagnosis, or treatment. It is general information about how the microbiome develops and is not guidance for treating an infant, child, or adult, and it does not diagnose or treat any condition. Decisions about infant feeding, delivery, antibiotics, or a child's health should be made with a qualified healthcare professional or pediatrician. Dietary supplements are not reviewed or approved by the US Food and Drug Administration for effectiveness before they are sold, and products containing Akkermansia muciniphila are intended for adults and adolescents aged 12 and over under existing international regulatory clearances; they are not intended for infants or young children. If you are pregnant or nursing, are immunocompromised, take medication, or are managing a health condition, consult a qualified healthcare professional before starting a probiotic or changing your diet or your child's diet.

Last reviewed: August 2026