Parenting by Experiment or Evolved Nest Companionship?

How do parents decide what research to follow in child raising? 


  • Adults need to understand the nature of a baby and her needs.
  • The problem with experiments on babies.
  • How to evaluate a research study.
  • How to assess parenting books.

Watch the presentation this post accompanies below.

Parents and adults generally from industrialized nations often misunderstand babies and their development. They are encouraged to look to “experts” and experiments to figure out how to treat young children, even though the experts may not be experts in child development (e.g., Oster, 2019). As mentioned in a prior post, Jean Liedloff was the first to challenge the appropriateness of this approach to parenting after her experiences with the Ye’quana in the Amazon rainforest. What are industrialized parents and adults to do?

Here are four pieces of advice from this expert.

  1. Understand the nature of a baby and her needs.

Babies resemble fetuses until 18-21 months of age (Leakey, 1996; Montagu, 1968, 1970; Trevathan, 2011).  They have high but decreasing malleability and plasticity neurobiologically, psychologically, and socially across the first years of life. The first 5 years shape the trajectories for neurobiological systems in terms of self-confidence, wellbeing, personality, sociality, and intelligences (e.g., social, emotional, cognitive, spiritual).

There are sensitive and critical periods for the development of different systems. Early life stress is a hidden trauma that is toxic to developing systems (Garner et al., 2021; Lanius, Vermetten & Pain, 2010; Shonkoff & Garner, 2012; Schonkoff & Phillips, 2000).

2. Learn about our species’ Evolved Nest.

Babies expect what our ancestors adapted to, what helped them survive, thrive and succeed across generations—our evolved nest. Because they are so immature, human babies evolved to expect their needs to be met immediately, which optimizes growth and development.

The evolved nest is a set of social and ecological circumstances typically inherited by members of a given species (Oyama et al. 2001). The evolved nest importance is found in the converging evidence of several sciences: evolutionary, ethology, ethnography, neuroscience, clinical and developmental studies. Most components have been conserved for over 70 million years, reaching us through the social mammal line. The evolved nest includes:

  • Soothing pre- and peri-natal experiences
  • Breastfeeding on request for several years
  • Affectionate (moving) touch, and no negative touch
  • A welcoming social climate
  • Self-directed free play with multiple-aged mates
  • Responsive relationships
  • Multiple responsive stable supportive caregivers
  • Nature immersion and connection
  • Routine healing practices

Every evolved nest component contributes to healthy brain development (e.g., Luby et al., 2012; Narvaez, 2014; Narvaez et al., 2013). The evolved nest initially acts like an external womb — meeting needs of child immediately to keep brain chemistry optimal. Babies (0-3) require nested companionship care to grow optimally.

Because humans are born so immature, much of our humanity develops postnatally (Narvaez, 2014). A toxically stressed baby does not grow the vast social brain our ancestors evolved, leaving them more stress reactive (e.g., Lupien et al., 2009). Animal studies show lasting effects on gene expression (e.g., Meaney, 2001).

The Evolved Nest prioritizes baby’s wellbeing for the long term & effects on society. Any move away from evolved practices is considered a risk factor.

3. Understand the problem with experiments on babies.

You can’t really do experiments on babies.

  • It is unethical. You should not randomly assign babies to treatments that may harm them.
  • Every baby develops at her own rate and is a different baby every few minutes (the entanglement of nature and nurture), so you cannot generalize results in any specific way.
  • You can create poorly constructed ‘experiments’ (poor design, poor monitoring, not blinded, not controlled). For example, the “intent to treat” method (ITT) often used in medical research testing drugs, but also in sleep training research. ITT is a method intended for drug trials but misused for baby studies. It ignores noncompliance, withdrawal, and anything that happens after randomization to a treatment group. In psychology, we know that fidelity of implementation is a key factor in judging whether a particular intervention worked as intended.
  • What is missing in virtually every study that advocates unnested care for babies (e.g., sleeping alone) is a comparison with our species’ baseline for what is normal, what babies need—the practices and outcomes of the evolved nest.

You can do animal studies. Most of the information on the effects of missing pieces of the nest are done on animals who are kept in cages (e.g., Harlow, 1958) or whose brains can be cut up afterward (e.g., Meaney, 2000). Since we are mammals too, we can draw conclusions on similarities in brain development and function.

See the Table Comparing Two Approaches to Parenting.

4. Learn about how to evaluate a research study.

Science is a tool. It has many aspects. It’s important to have a broad scope understanding of science. Some sciences are more observational and descriptive (e.g., anthropology, biology), some are experimental (e.g., physics, chemistry) and others use a combination of methods (e.g., psychology). Each science attempts to have rigorous tools for assessing valid study designs and methods, as well as analyses and interpretations of findings. In assessing what is good for a human being, you need to take into account multiple branches of science that study human outcomes: evolution, ethology, archeology, anthropology, neuroscience, clinical, developmental. “Evidence based” for deciding about meeting babies’ needs must mean including a broad sweep of information from across relevant sciences.

  • Understand that experimental studies of rapidly developing babies provide limited information. They isolate variables and test people in unusual ways, making it hard to apply to real life where every individual is unique, dependent on relationships, and everything about a person & relationships interact.

Assess how researchers are using the tools of science:

  1. Do the researchers “have skin in the game” (i.e., they depend on the study outcomes for their income, reputation, their group’s or their funder’s ideology)?
  2. Overall, do the conclusions fit with our species history, needs, development, and known clinical outcomes?
  3. Do the results examine the long-term outcomes across years into adolescence and adulthood in terms of multiple health outcomes?
  4. Do the results fit with your heart-of-heart instincts for what is best for your child? Parents have built-in instincts that evolved too!

5. Learn how to assess parenting books.

  1. What credibility does the author have? Do they have a deep understanding of child development?
  2. What biases does the author have? Does she make them explicit?
  3. What baselines (for what is normal) does the author adopt? Does she make her assumptions explicit? Do these fit with our species history, needs, development, and known clinical outcomes?
  4. Does the author provide specific details for study references (empirical evidence) for conclusions drawn? (Allows readers to look at the studies and draw own conclusions.)
  5. Is there converging evidence from a broad science perspective for the findings cited? 
  6. Do the author’s conclusions fit with our species history, needs, and clinical outcomes?

Take home message: Our species’ evolved nest provides appropriate baselines, proven adaptive over millions of years. Findings from a few “experiments” cannot compete. Thus, it is appropriate to question the findings of studies that conclude that violations of evolved nest practices are ‘safe.’


Garner, A., Yogman, M., Committee on Psychosocial Aspects of Child and Family Health, Section on Developmental and Behavioral Pediatrics, Council on Early Childhood. (2021). Preventing childhood toxic stress: Partnering with families and communities to promote relational health. Pediatrics, 148(2), e2021052582

Harlow, H. (1958). The nature of love. American Psychologist, 13, 673-685.

Lanius, R. A., Vermetten, E., & Pain, C. (2010). The impact of early life trauma on health and disease: The hidden epidemic. New York, NY: Cambridge University Press.

Luby, Joan L., Deanna M. Barch, Andy Belden, Michael S. Gaffrey, Rebecca Tillman, Casey Babb, Tomoyuki Nishino, Hideo Suzuki, Kelly N. Botteron (2012). Maternal support in early childhood predicts larger hippocampal volumes at school age. Proceedings of the National Academy of Sciences, 109(8), 2854-2859.

Meaney, M. J. (2001). Maternal care, gene expression, and the transmission of individual differences in stress reactivity across generations. Annual Review of Neuroscience, 24, 1161–1192.

Montagu, A. (1968). Brains, genes, culture, immaturity, and gestation. In A. Montagu (Ed.), Culture: Man’s adaptive dimension (pp. 102-113). New York: Oxford.

Montagu, A. (1986). Touching: The human significance of the skin. New York: Harper & Row.

Narvaez, D. (2014). Neurobiology and the development of human morality: Evolution, culture and wisdom. New York: Norton.

Narvaez, D., Panksepp, J., Schore, A., & Gleason, T. (2013). Evolution, early experience and human development: From research to practice and policy. New York: Oxford.

Oster, E. (2019). Cribsheet: A data-driven guide to better, more relaxed parenting, from birth to preschool. New York: Penguin Press.

Oyama, S., Griffiths, P.E., & Gray, R.D. (2001). Cycles of contingency: Developmental systems and evolution. Cambridge, MA: MIT Press.

Shonkoff, J. P., & Garner, A. S. (2012). The lifelong effects of early childhood adversity and toxic stress. Pediatrics, 129(1), e232-246. doi: 10.1542/peds.2011-2663

Shonkoff, J. P., & Phillips, D. A. (2000). From neurons to neighborhoods: The science of early childhood development. Washington DC: National Academy Press.

Suttie, I. (1935). The origins of love and hate. New York, NY: The Julian Press.

Trevathan, W.R. (2011). Human birth: An evolutionary perspective, 2nd ed.. New York: Aldine de Gruyter.

There is a lot of misinformation about babies and their needs, and parents are often encouraged to ignore baby’s signals. Bad idea. Babies are “half-baked” at birth and have much to learn with the help of physical and emotional support from caregivers. Taking care of baby’s needs is an investment that pays off with a happier, healthier child and adult. Here are 28 days of reminders about babies and their needs. Discover the Evolved Nest’s 28 Days of Baby Care here.
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