Homo sapiens

Homo sapiens is the species to which all living humans belong.

Humans are primates in the great-ape family Hominidae, with evolutionary origins in Africa and a present distribution across the world.

The human body plan supports habitual movement on two legs, with the head balanced above the spine and the hips and knees carrying weight during upright walking.

The curve of the lower spine helps absorb the mechanical stresses of walking.

Compared with many earlier human forms, modern humans generally have a lighter skeleton, a high skull vault, a relatively vertical forehead and a smaller, less projecting face.

Human reproduction involves the union of sperm and egg, followed by development of an embryo that implants in the lining of the uterus.

During pregnancy, the placenta supports exchange of oxygen and nutrients and removal of waste products.

Its branching villi develop as the fetus grows, creating an extensive exchange structure rather than a simple container around the fetus.

Pregnancy is commonly dated as about 40 weeks from the last menstrual period, a convention that starts before fertilization rather than at it.

After birth, human milk can supply fats, proteins, carbohydrates, vitamins and minerals during early development.

Later, puberty brings sexual maturation, a major transition between childhood and reproductive adulthood.

Human ways of obtaining food have included gathering plants, hunting animals and fishing with specialized tools.

Fire, clothing and shelters helped people occupy different environments, while social networks enabled the exchange of resources over wide areas.

Human material culture also includes art, music and symbolic objects.

Over the last roughly 12,000 years, farming and herding have transformed many landscapes and relationships with other species, without describing the way of life of every human community.

Human nuclear DNA is packaged with proteins into chromosomes; the usual chromosome complement in a body cell is 23 pairs.

Egg and sperm normally contribute one set each, bringing together genetic material inherited from both parents.

This shared organization does not make every human genome identical: a single reference sequence cannot represent all human genetic variation.

A 2022 study filled major gaps in a human reference assembly, producing chromosome sequences that excluded the Y chromosome.

A different approach, described in 2023, combined phased genome assemblies from 47 individuals into a draft pangenome reference.

Using multiple genomes provides a way to study sequence differences that comparison with one reference can miss.

NCBI Taxonomy assigns identifier 9606 to Homo sapiens at species rank, but a taxonomy record is not a genome assembly or a sample from every population.

The 2023 pangenome study represents 47 diploid individuals as 94 haplotype assemblies, keeping the paired chromosome sequences distinct.

The authors discuss the benefits of broader representation while identifying continued work on validation and challenging genomic regions.

The 2022 T2T paper’s abstract explicitly excludes Y from its assembled chromosome set.

The 2023 pangenome methods describe a later T2T-CHM13 v2.0 reference that includes a Y chromosome from HG002, which they excluded from the stated segmental-duplication reliability analysis.

Consequently, the study year, reference version and donor origin must accompany a statement about whether that reference includes Y.

Placental development includes remodeling of maternal uterine blood vessels by cells associated with the placental villi.

The growth and branching of villi connect the placenta’s changing structure with the exchange needs of the developing fetus.