What Other Species Reveal About What Makes Us Human
Have you ever watched a toddler take their first steps and wondered how this milestone compares to when other animals learn to walk? Or considered why human childhood lasts so much longer than that of our closest primate relatives? These questions lie at the heart of a fascinating scientific field called comparative human development, which seeks to understand human uniqueness by studying how we develop in comparison to other species 2 .
By examining the pace and pattern of cognitive growth across different animals, scientists are beginning to unravel some of biology's most profound mysteries.
The story of human development is deeply interconnected with the development of life itself, transforming our understanding from education to neurological disorders 2 .
Comparative developmental psychology sits at the intersection of two established fields: developmental psychology and comparative psychology 2 . When combined, they offer powerful insights unavailable to either approach alone.
For decades, scientists struggled to study the living human brain in action, especially during its earliest developmental stages. Mental disorders like autism and schizophrenia were particularly mysterious 7 .
Stanford neuroscientist Dr. Sergiu Pasca pioneered creating three-dimensional human brain circuits in the laboratory to study Timothy syndrome.
Researchers began with a simple skin biopsy from individuals with Timothy syndrome and healthy controls.
Using induced pluripotent stem cell technology, they reprogrammed skin cells into stem cells.
Stem cells were guided to develop into specific types of brain cells and 3D brain organoids.
Creating "assembloids" by combining different brain region organoids to observe neural migration 7 .
| Observation | Healthy Models | Timothy Syndrome Models | Significance |
|---|---|---|---|
| Neuron Migration | Organized, directional | Disorganized, misrouted | Supports circuit imbalance theory of autism |
| Circuit Integration | Balanced excitatory/inhibitory input | Imbalanced connectivity | Reveals potential mechanism for sensory issues |
| Intervention Response | Normal development | Corrected migration with treatment | Offers potential therapeutic pathway |
| Tool/Technology | Function | Application Example |
|---|---|---|
| "Twist Ancient DNA" Reagent 6 | Enriches ancient DNA samples | Comparing genetic development across evolutionary time |
| Neural Organoids 7 | 3D cell cultures mimicking brain regions | Studying human-specific neural development |
| Assembloids 7 | Combined organoids forming neural circuits | Modeling interactions between brain areas |
| Induced Pluripotent Stem Cells 7 | Reprogrammed adult cells | Generating patient-specific neurons for study |
| Initiative | Lead Institution | Primary Focus |
|---|---|---|
| BRAIN Initiative® 1 | NIH | Understanding neural circuits |
| Rice Brain Institute | Rice University | Integrating engineering and neuroscience |
| Brain Organogenesis Center 7 | Stanford University | Human-specific brain development |
The BRAIN Initiative® has explicitly identified the need to consider "neural enhancement, data privacy, and appropriate use of brain data in law, education and business" 1 .
Similarly, the creation of human brain organoids prompts questions about the ethical status of these increasingly complex neural tissues 7 .
Large-scale collaborative efforts bring together engineers, biologists, psychologists, and ethicists to advance the field responsibly 1 .
The Rice Brain Institute uniquely leads with engineering rather than traditional neuroscience, developing technologies that can interface directly with the brain .
New approaches for neurological and mental health disorders
Learning strategies informed by brain development
Neural sensors and rehabilitation robotics
Sharing brain data across research institutions
Comparative human development reveals that our unique human capacities emerge not from mysterious ingredients, but from changes in the timing, pattern, and context of processes we share with other species.
The prolonged journey of human childhood, once viewed simply as a biological constraint, now appears as a critical period that enables our exceptional learning abilities and cultural capacities to unfold.
As research continues to bridge species and disciplines, we move closer to understanding not just how we become human, but how we might better support human flourishing across the lifespan.