• 3D racial spectrum
    The metaphor of outward human appearances as a constantly churning worldwide continuum, rather than fixed categorical "races".
  • abiogenesis
    The chemical advances that crossed the line from non-living chemistry to life.  LIterally, "the creation of life from non-life".  This only occurred once or a limited number of times on early Earth.
  • Acheulean
    (a-SHOO-le-an) The stone age industry associated with hand axes, about a million years ago.
  • aerobic respiration
    A cellular metabolic process that burns oxygen for energy.  Our cells do this, which is why we breathe.
  • anatomically modern human
    One definition of Homo sapiens, meaning humans who resemble living people more than they resemble extinct early humans.
  • AMH
  • amniote
    Land animals whose embryos develop in protective membranes: Reptiles, birds, and mammals.
  • anaerobic
    Without oxygen
  • anaerobic respiration
    A certain metabolic process that gives cells (such as some bacteria) energy without oxygen.
  • animism
    The belief or outlook that nature is animated by outside spirits.  This outlook is so deeply embedded into human assumptions about the world that there is no pre-modern word for it.
  • anthropic principle
    The principle that present conditions have "backward predictive" power about past circumstances.  So named because the universal "present conditions" are those that support human life on Earth.  Often misunderstood; just because past conditions "must" be consistent with the present (a future constraint) doesn't mean they "must have" happened in the first place (a past or predictive constraint).
  • anthropology
    The over-arching study of humans, including ancestral and related apes.
  • arboreal
    Living in trees
  • archaea
    Prokaryotic cells that are structurally similar to, but chemically different from, bacteria.
  • archaeology
    The study of human-made artifacts
  • Archean
    The Archean Eon, 2.5 - 3.8 BYA, was defined by solidification of the Earth and prokaryotic life.
  • Ardi
    The best-known specimen of an Ardipithecus, a female of species Ardipithecus ramidus.
  • Ardipithecus
    A hominin genus that lived 4 - 6 MYA in Ethiopia.
  • atheist
    Not religious, esp. not holding a belief in God, gods, or spirits.
  • atom
    The smallest unit of matter that is (usually) stable.  It consists of a nucleus of protons and neutrons, surrounded by electron clouds.  There are about 100 kinds of atoms, the elements of chemistry.
  • ATP
    One of the most important macromolecules for storing energy in cells.  Stands for Adenosine Tri-Phosphate
  • Aurignacian
    The first modern human culture in Europe, also found in the Levant, roughly 30,000 - 40,000 years ago.
  • Australopithecus
    (AWE-struh-lo-PITH-a-cus) A hominin genus found in Africa 1 - 4 MYA, believed to be ancestral to the first humans.
  • bacteria
    The oldest, smallest, and simplest form of life. Each bacterium is one cell, though bacteria often form colonies.
  • basal
    "At the base" of a phylogenetic tree.  This may refer to a species that lived long ago, or a living species that still resembles such an older one.
  • Beringia
    The geographic region where Asia (Siberia) meets North America (Alaska).  Currently submerged, Beringia is above sea level during some ice ages, and has formed a land bridge between these continents at various times.
  • big bang
    A physical event that marked the beginning of the known universe.  It is called a "bang" because it started small and then expanded rapidly, and in fact the universe is still expanding.
  • big data
    Data, generally procured from internet activity, that is too large for a single computer to handle.  A central resource in the system of checks and balances among consumers, large corporations, and governments.
  • biped
    An animal that walks on two legs.
  • bonobo
    Pan paniscus, a species of chimpanzee also sometimes called "pygmy chimps".  There are subtle physical differences and major behavioral differences between "common" chimps and bonobos.  The two species were permanently separated by the Congo River 1 - 3 MYA.
  • brachiate
    To hang and / or swing by the arms.
  • bronze age
    The period of time in which a culture's most advanced tools and weapons were bronze.  Differs by region.  The most important bronze ages were 3 - 7 TYA in the Old World.
  • BYA
    Billion Years Ago
  • Byzantium
    Byzantium:  The city now known as Istanbul, Turkey, as it was named before the 4th century. Byzantine: The exonym / retronym for the eastern Roman Empire (4th - 15th centuries) with its capital at the city formerly known as Byzantium, then renamed as Constantinople.
  • Cambrian explosion
    The earliest widespread proliferation of macroscopic animals with mineralized body parts, roughly 540 MYA.  For paleontologists, it is the moment that fossils seem to have "burst onto the scene".
  • canines
    The teeth that are third from the center line in the human jaw; canines are "fangs" in non-human apes, carnivores, and many other animals. Dogs (the teeth are named after the dogs).
  • carbohydrate
    An organic molecule formed from carbon, hydrogen, and oxygen.  Fibers, starches, syrups, and blood sugar are carbohydrates.
  • Carboniferous
    The geological period of 300 - 360 MYA, characterized by the first large forests, many of which formed coal deposits upon their death.
  • caste
    A class in India's social system.
  • catarrhine
    The clade including apes and Old World monkeys.  Humans are catarrhines.
  • Cenozoic
    The present era of geological time, dating back to the extinction of the dinosaurs about 66 MYA.
  • cerebellum
    The part of the brain responsible for control of voluntary movements.
  • chemistry
    The study of atomic interactions in the formation of matter.
  • chiefdom
    A level of social organization intermediate between a clan and a civilization, characterized by one or several villages under the command of a hereditary chief.
  • chordate
    A phylum of animals that is slightly more broad than vertebrates.  Humans are chordates.
  • chromosome
    A continuous string of DNA found in the nucleus of eukaryotes.
  • civilization
    A stably unified polity with population on the order of 100,000 or more, including at least one city on the order of 10,000 or more.  Most historians attempt to define civilizations by their achievements, but those achievements are either the direct result of large populations or are not common to all polities commonly referred to as civilizations.
  • clade
    A biological grouping based on actual genetic descent rather than physical similarities.
  • Clovis
    The first widespread American culture.  Concentrated in the southeastern US and characterized by fluted arrowheads 13,000 years ago.
  • communism
    The economic ideal of a society living as a commune, with no government, class structure, or private property.  In practice, only realized by hunter-gatherers and very small communities.  Confusingly, the most socialist governments call themselves "communists" euphemistically.
  • conspiracism
    The belief that reality is controlled or concealed by agents in a secret realm.
  • Constantinople
    The city now known as Istanbul, Turkey, as it was named from the 4th - 15th centuries as the capital of the Eastern Roman or "Byzantine" Empire.
  • cortex
    The outer layer of the brain, which plays a role in higher-level conscious thought.
  • cranium
    The dome of the skull, containing the brain.
  • Cretaceous
    The last geological period of the Mesozoic (dinosaur) era, roughly 65 - 145 MYA.
  • Cretaceous-Paleogene
    The mass extinction that ended dinosaur life and led to the mammalian radiation about 70 MYA.
  • Cro-Magnon
    The first Homo sapiens in Europe, around 40 TYA.
  • cultural adaptation
    A non-biological way of dealing with natural challenges (beaver dams, human air conditioning).
  • culture
    Goods and ideas that can spread among people with or without political organization.
  • cyanobacteria
    The most important photosynthesizing bacteria, aka "blue-green algae".
  • Denisovan
    A species of early human most closely related to Neanderthals, once widespread in Asia.
  • deuterostome
    A superphylum of animals defined by its embryonic development; the anus appears first and the "mouth second", which is the literal meaning of the word.  Chordates, and therefore humans, are deuterostomes.
  • dimorphic
    Having two different sizes / shapes, especially between the sexes of a single species.
  • DNA
    Deoxyribo-Nucleic Acid, a macromolecule found in every living cell from conception, which contains the information necessary for that organism to develop.
  • dopamine
    A hormone / neurotransmitter that is primarily associated with reward or pleasure in the mammal brain.
  • early humans
    Extinct species of the Homo genus; all humans but sapiens.
  • ecosystem
    A community of plants, animals, and other organisms interacting with each other and with their environment.
  • egalitarianism
    A social structure without class or hierarchy, in which all members play nearly identical roles.
  • electron
    A fundamental particle with negative charge.  Electrons make up the outsides of atoms, and their interactions define chemical reactions.  The free movement of electrons is electricity.
  • enamel
    The outer layer of teeth.  Enamel is a mineral, the hardest part of the body.
  • endosymbiosis
    A symbiotic relationship formed when one organism lives inside another.  The most important example was when bacteria became mitochondria within eukaryotic cells.
  • eon
    The longest unit of geological time, spanning hundreds of millions or billions of years.  Not a constant duration.  Scientists divide the history of Earth into four eons according to overall characteristics of the planet and its life.
  • epistemology
    The philosophy of truth, knowledge, and belief
  • epoch
    The fourth-longest unit of geological time, generally spanning tens of millions of years.  Recent epochs (which are the only ones to be concerned about) end in the suffix -cene.
  • erect bipedalism
    Walking on two feet and with an upright back.
  • erectus
    One of the earliest human species, ranging across Africa and southern / eastern Asia roughly 2 MYA - 300 TYA.  In this book, erectus includes ergaster, an early African version sometimes classified as a separate species.
  • ergaster
    The African branch of Homo erectus.  H. ergaster is believed to be the common ancestor of many human species including H. sapiens.
  • eukaryote
    An organism with large nucleated cells; not bacteria.  Protists, fungi, plants, animals.  Humans are eukaryotes.
  • evidence filtering
    The instinctive tendency to form a preconceived belief and then (1) Construe any evidence consistent with the belief to prove that belief, and (2) Non-falsify or make up excuses to ignore evidence inconsistent with the belief.  The psychological term is "assimilation bias"; "evidence filtering" coined by SF.
  • evolutionary pressure
    An environmental condition that favors one particular inheritable trait over another one, thus allowing the favored trait to be more rapidly reproduced.
  • exonym
    A name for a nation that is used by foreigners, not by the nationals themselves.
  • fallacy
    False logic
  • falsify
    To prove a hypothesis false (or likely to be false) with evidence.
  • Fertile Crescent
    The region of historically fertile riverbeds arcing from Egypt in the southwest to Syria in the north and then to Iraq / Iran in the southeast.
  • floresiensis
    The "hobbit" species of early humans known only from the island of Flores, Indonesia.
  • forage
    To search widely for food, i.e. to hunt animals and / or gather wild edible plant matter over a wide range.
  • fossil fuel
    Coal, petroleum, and natural gas: hydrocarbon fuels, with prehistoric biological origins, that are now mined from the Earth.
  • fundamental particles
    The smallest, simplest, indivisible particles of matter and energy.
  • gene
    A snippet of DNA that is directly used to synthesize a protein.
  • gene flow
    The exchange of genes between populations of a species.  It can be a result of migration, continuous mating across a large region, or even occasional cross-breeding / intermarriage.
  • gene pool
    The set of genes shared within a species, hypothetically available to all members of the next generation through mating.
  • generalist
    The opposite of a specialist.  A species is a generalist if it is well-adapted to a wide variety of conditions.
  • genome
    The complete description of DNA for an individual or species.
  • genus
    The biological classification level above species; multiple species grouped together by common ancestry and / or similar appearance.
  • geography
    The physical layout of landforms, water, air, and their resources, sometimes in the context of political boundaries.
  • geology
    The study of Earth's history: layers, features, and the processes that formed them.
  • glossary
    A mini-dictionary for the specialized terms within a book.
  • glossary entry
    A definition that I will provide for certain terms within this book, for terms that are obscure / technical or that require careful definition for meaningful discussion.
  • glycolysis
    One of the oldest metabolic pathways, performed by almost every cell.  The breakdown of glucose to form ATP.
  • gracile
    Thin-boned; the opposite of robust.
  • Gulf Stream
    A warm Atlantic current from the Gulf of Mexico to the Arctic Circle via North America and Europe.
  • habilis
    The first species that is generally accepted as human.  Southern and eastern Africa 2 MYA.  Made Oldowan tools.  Making a transition to the human nose.
  • haplogroup
    A clade of people as characterized by a shared genetic marker, especially mutations of the Y chromosome or mitochondrial DNA going back 10,000 - 300,000 years.
  • heidelbergensis
    An early human species ranging across Africa and Europe, currently seen as a viable common ancestor for modern humans and Neanderthals.
  • Holocene
    The present geological epoch, beginning with the end of the most recent ice age 12,000 years ago and continuing until the next ice age in the future.  Also called the present interglacial or Marine Isotope Stage 1.
  • hominin
    Humans and the extinct species that are more closely related to humans than to any other living species.
  • Homo
    The genus consisting of all past and present human species, dating back approximately 2 MYA.  Homo differs from its parent genus, Australopithecus, mostly in Homo's larger braincase and more widespread tool use.
  • honing
    A form of chewing in which the canines rub up against pre-molars of the opposite jaw to keep the canines sharpened.
  • horizontal gene transfer
    A non-reproductive exchange of DNA between similar organisms like bacteria.  Called "horizontal" because it is not associated with a "vertical" descent down a family tree but rather stays within the same generation.
  • humanism
    A point of view centered on humans rather than gods.
  • identity politics
    The interest in politically organizing people based not on historic nationality but on certain minority status within a nation, such as coloration or sexuality.  There is generally a perceived sense of social inequality and a mission to overcome it.
  • incisors
    The wedge-shaped, "scraping" teeth at the front of the mouth; first and second from the center line in the human jaw.
  • Industrial Revolution
    The technological explosion enabled by burning fossil fuels.
  • interglacial
    A warm period between glacial episodes in an ice age.
  • iron age
    The period of time in which a culture's most advanced tools and weapons were made of iron.  Differs by region.  The first iron ages date to -1200 in western and southern Eurasia.  There is no definite end to the iron age, but the term fades out gradually in the 1st millennium in light of gunpowder and overshadowing historic events.
  • Jurassic
    The middle geological period of the Mesozoic (dinosaur) era, roughly 145 - 200 MYA.
  • Kenyanthropus
    A proposed genus for a flat-faced hominin living 3.2 - 3.5 MYA in Kenya, near the Lomekwian tool site.
  • knapping
    Striking stones together in such a way as to shape them into useful tools.
  • KYA
    Kiloyears ago (thousands of years ago)
  • Levant
    The eastern shoreline of the Mediterranean Sea
  • light year
    The distance that light travels in a year. Approximately 9 trillion kilometers or 6 trillion miles.
  • light-year
    The distance that light travels in a year.  On the order of ten trillion kilometers.
  • Linnaean
    The 18th century system of classifying living things by their physical similarities rather than common ancestry.  Named for its creator Carl Linnaeus, this system gave us the classic divisions of kingdom, phylum, class, order, family, genus, and species, and the binomial Latin nomenclature of "scientific names" such as Homo sapiens.
  • lipids
    A class of fat / oil molecules found in all living things
  • logarithmic
    Counting multiplications rather than additions.  This entire book is a logarithmic history because each chapter spans ten times as many years as the next one in the same number of pages.
  • Lomekwian
    The oldest known stone age industry, known from only one site near Lomekwi, Kenya, and dated to about 3 MYA.
  • macromolecule
    A very large molecule, esp. one of the four classes of molecules that make up living things: carbohydrates, lipids, proteins, and nucleic acids.
  • macroscopic
    Opposite of microscopic; large enough to be visible to human eyes.
  • magic willpower
    The natural human explanation for causes that we don't understand.  We assume that natural phenomena occur because spirits or gods want them to.  We offer no mechanism for explaining how this willpower causes action; it's just magic.  Ancient people probably never saw need for explanation because they were not conscious of any intermediaries between their own willpower and action.  -- This term coined by Scot Fagerland
  • Marine Isotope Stage
    A glacial or interglacial period as defined by evidence found in the ocean.  Interglacials have odd MIS numbers and glacials have even numbers.  Present time is MIS 1.
  • maternal
    Relating to the mother
  • meiosis
    The cellular process that produces sex cells (eggs or sperm) from specialized germ cells
  • meme
    A cultural unit of reproduction; knowledge, behavior, or belief that can be transmitted from person to person.  Memes compete and evolve in the "meme pool".  Dawkins 1976.
  • Mesoamerica
    The geographic region also known as "Central America", from Mexico to Panama.
  • Mesolithic
    The narrow period defined by small stone tools and the first settler-cultivators, roughly 7 - 12 TYA.  Also sometimes called the epipaleolithic.
  • Mesozoic
    The "middle" era of animal life, between the mass extinctions of 250 and 65 MYA.
  • metabolism
    The chemical activity that an organism must perform to sustain itself; extracting matter and energy from the environment to build itself.  For animals, this essentially amounts to eating, drinking, and breathing.
  • metazoa
    Animals with tissue, which includes all animals except sponges.
  • microbe
    A microscopic living thing; essentially a single-celled organism.
  • Middle Stone Age
    The period of medium-advanced stone technology, roughly 50 - 250 TYA, especially in Africa where our Homo sapiens and heidelbergensis ancestors lived.
  • Milankovitch Cycles
    Astronomical cycles related to Earth's orbit around the sun.  They affect climate on time scales of 10,000 - 100,000 years and have been especially impactful during the present ice ages.
  • Miocene
    The first epoch of the Neogene Period, spanning roughly 23 - 5 MYA.  Characterized by global cooling and the evolution of apes.
  • mitochondria
    Organelles that burn oxygen for energy in every eukaryotic cell.
  • mitochondrial DNA
    The genome of the mitochondria within cells.  It is passed down from mother to child.
  • molars
    Large teeth at the back of the jaw; 6th - 8th from the center line in the human jaw.
  • molecule
    Two or more atoms bonded together as a discrete unit.  A molecule is the basic unit of a compound such as water.
  • monophyletic clade
    A closed and complete line of descent, consisting of a particular ancestor and all of its descendants.
  • Moore's Law
    Intel co-founder Gordon Moore's observation that the number of transistors on a cutting-edge computer chip has doubled every 1 - 2 years, and his prediction that this rate of growth will continue as long as possible.
  • multiregional
    A form of evolution that takes place in humans or another species with a very large geographic distribution but no distinct boundaries.  Gene flow is just fast enough to maintain one gene pool, but too slow to homogenize genetic differences between regions.
  • mutation
    An "error" in the replication of an organism's DNA, resulting in a new genetic sequence that is passed down to its descendants.
  • MYA
    million years ago
  • MYO
    million years old
  • naledi
    An early human species found in South Africa 200 - 300 TYA.
  • nationalism
    Originally, nationalism was the call for nations to be self-determined, free from empires, kings, and / or the Catholic Church. Increasingly today, "nationalism" refers to protectionism and the prioritization of national over global interests.
  • natural religion
    The religious instincts, beliefs, and behaviors that characterized modern humans before civilization.
  • Neanderthal
    A species of early human ranging across Europe and central Asia roughly 300 - 30 TYA.
  • neocortex
    The highly-developed outer layer of the mammalian brain. Responsible for advanced motor-sensory functions and social intelligence / emotions.
  • Neogene
    The second period of the present Cenozoic Era, spanning roughly 3 - 23 MYA.
  • Neolithic
    The "new stone age", an archaeological term.  Characterized by polished stone tools and the earliest agriculture, until the advent of metallurgy.  Began as early as 10 TYA in some regions.
  • neuron
    A cell of the brain and nervous system.
  • neurotransmitter
    A chemical in the brain or nervous system that is required for signals to pass between neurons.
  • neutron
    A subatomic particle with no electric charge.  Neutrons are found in the nuclei of atoms.  Each neutron is made of three quarks.
  • Norte Chico
    The earliest recognized civilization in South America, centered around Caral, Peru in the -4th to -2nd millennia.
  • nuclear DNA
    The DNA found within the nucleus of every cell of a eukaryotic organism, providing the codes for synthesizing all the proteins that make up that organism.  It includes the X and Y chromosomes but not mitochondrial DNA.
  • nuclear family
    A family unit consisting of two parents and their biological children, living separately from the rest of their community and relatives.
  • nucleosynthesis
    The fusion of protons and neutrons to form nuclei of atoms.  Nucleosynthesis only occurs in the big bang, stars, supernovae, and hydrogen bombs.
  • obligate
    Compelled by physiology, such as a fish being an obligate water-breather while an amphibian can choose air or water.
  • Oldowan
    The earliest widespread stone age industry, characterized by pebble tools.
  • Oligocene
    The last epoch of the Paleogene Period, spanning 34 - 23 MYA.
  • Olmec
    The earliest recognized civilization in Mesoamerica, centered around gulf coast Mexico in the -2nd to -1st millennia.
  • omnivore
    An animal that eats large percentages of both plant and animal products.
  • opisthokont
    A eukaryotic cell that propels itself forward with a single tail in the rear, or an organism that has such cells.  Humans are opisthokonts, with sperm being the opisthokontic cell.
  • empire
    A polity organized under one state authority, but spanning multiple nations.
  • organized religion
    A moral code that is specific to a particular society, organized by the state, and ultimately enforced by a standardized belief in moralizing gods.
  • orogeny
    The formation of mountains, especially when continental plates collide.
  • Paleogene
    The first period of the present Cenozoic Eon, spanning 66 - 23 MYA.
  • Paleolithic
    The stone age, especially as manifested in Europe and Asia.
  • paleontology
    The study of fossils.
  • Paleozoic
    The first era of the present Phanerozoic Eon, the era of "old fossil life", roughly 300 - 500 MYA.
  • Pangaea
    The super-continent that existed about 300 MYA when essentially all continental crust was lumped together.  Literally "all land".
  • paternal
    Relating to the father.
  • pathogen
    A bacteria, virus, or similar microorganism that causes diseases.
  • pathway
    A series of chemical steps used by a cell to perform vital life functions.
  • patrilineal
    Tracing descent (or rank or property etc.) through the male line.
  • Pax Republica
    The military peace that has predominated among republics since WWII.  Nearly every conflict since then has involved at least one dictator.  Term coined by Scot Fagerland as a play on Pax Romana.
  • Permian
    The last geological period of the Paleozoic (old life) era, about 250 - 300 MYA.
  • Permian-Triassic
    The largest mass extinction of all time, around 250 MYA between the Permian and Triassic periods.
  • Phanerozoic
    The present eon of geological time, dating back to the Cambrian Explosion about 540 MYA.  Characterized by macroscopic organisms with hard body parts.
  • photon
    A particle of light
  • photosynthesis
    The exploitation of solar energy in living things, especially by plants and cyanobacteria to make glucose.
  • phylogeny
    "Family tree" analysis on the evolutionary time scale; the relationships of living things at the levels of species and higher.
  • phylogeography
    Long-term patterns of population descent and migration, as revealed by DNA testing.
  • phylum
    A category of living things that is smaller than a kingdom (like animals) but larger than a class (like mammals).  In the animal kingdom, each phylum has a different body plan.  Humans belong to the phylum of chordates.
  • physics
    The study of space, time, matter, energy, and forces at their most fundamental levels, before getting to any emergent properties of complex things.
  • placental
    Mammals that have a uterus and give live birth.  Humans are placentals.
  • placoderm
    An extinct class of armored fish, probably ancestral to humans.
  • plasma
    Gas at such high temperature that atoms decompose into charged nuclei and electrons (e.g. in a star)
  • plate tectonics
    The movement of continents and seafloor on the surface of the Earth as a byproduct of three-dimensional churning in Earth's interior.
  • Pleistocene
    (PLICE-toh-seen) The geological epoch spanning roughly 3 MYA - 12 KYA.  Includes all of the Quaternary ice age cycles up until (and not including) the present interglacial.
  • Pliocene
    The shorter and latter epoch of the Neogene Period, spanning roughly 5 - 3 MYA.
  • polity
    A political body (village, city-state, nation, empire, etc.)
  • populism
    A form of politics unique to democracy, characterized by the sentiment that government is beholden to "corrupt elites" and must bow to the demands of "ordinary people" or the "righteous" citizens.
  • positive feedback
    A cycle by which a condition causes itself to increase, like sound picked up and increasingly amplified by a microphone / speaker system.
  • potential energy
    Energy that is stored up or contained and is not currently being used to excite matter.
  • prefrontal cortex
    The front tip of the brain, associated with personality and social / emotional intelligence.
  • prehensile
    Flexible and capable of grabbing.
  • premolar
    Teeth situated between the canine and the molars.  4th and 5th from the center line in the human jaw.  aka bicuspid
  • primate
    An order of mammals characterized by hands and forward-facing eyes.  Humans are primates.
  • primogeniture
    Succession of property and / or title to the first-born child
  • prokaryote
    The earliest form of single-celled life, like bacteria.
  • proteobacteria
    The bacteria that evolved the capability to "breathe" oxygen
  • Proterozoic
    The geological eon dominated by protists, roughly 2.5 BYA - 500 MYA.  Also defined by the appearance of continents, oxygen gas, and pre-fossil plant / animal life.
  • protist
    A eukaryote, usually single-celled, that is not an animal, plant, or fungus.
  • Proto-Indo-European
    A hypothesized culture and language that spread out to form today's Indo-European languages.
  • proton
    A subatomic particle with positive charge.  Protons are found in the nucleus of an atom, and they define which element that atom is.  Each proton is made of three quarks.
  • quantum
    At the level of fundamental particles. Derived from "quantity" because, when we view such particles at their own level, they are countable, not continuous.
  • quantum physics
    The study of matter, energy, and forces at the atomic and sub-atomic level.  At this level, matter and energy are not continuous but discrete.
  • quarks
    Fundamental particles that combine in triplets to produce protons and neutrons.  Quarks are never found in isolation, except perhaps in the very tiniest fraction of a second after the big bang.
  • Quaternary
    The geological period from about 3 MYA to the present.  Defined by the ice ages, including the present interglacial.
  • radiation
    (Physics):  Energy that is unbound to matter and moving at the speed of light. (Biology):  The divergence of multiple species from a common ancestor, usually quickly due to a rapid change of environment.
  • red ochre
    The earliest pigment known to have been used by humans.  Archaeologists associate pigment with modern behavior because it is used for ornamentation and because it requires processing.
  • Renaissance
    The mid 2nd millennium in Europe.  Literally "rebirth".  Characterized by rediscovery of pre-Christian literature, humanism, and a renewed interest in progress.
  • republic
    A form of government in which citizens elect public officials, who serve as representatives and legislators for a fixed salary.
  • RNA
    Ribonucleic acid.  A nucleic acid in every living cell that plays an important role as a go-between for DNA and proteins.
  • robust
    When referring to bones, "robust" means "thick and strong."  The opposite of gracile.
  • Sahelanthropus
    A very early hominin genus, found 6 - 7 MYA in Chad.
  • savanna
    The boundary between a grassland and woodland.  A favorite habitat of hominins and early humans.
  • secret trillionaire fallacy
    The illusion that something that's hard to understand or believe (like a billionaire) is satisfactorily "explained" by something that's objectively even harder to understand or believe (like a trillionaire) usually by appealing to human-like consciousness.
  • secular
    Not involved with religion
  • sediment
    A layer of rock, especially as laid down by minerals within water.
  • service economy
    The economy of services as opposed to goods.  Services range from common (housecleaning) to specialized (brain surgery) and computerized / high-tech (internet providers).
  • settler-cultivator
    The way of life that served as a transition between hunting-gathering and agriculture around 10 - 15 TYA.  Characterized by small and / or temporary settlements and the care, but not deliberate breeding, of plants and animals.  I coined this term in this book.
  • Shang
    The earliest Chinese dynasty known by name.  Yellow River Valley, -2nd millennium.
  • Shi'ite
    The branch of Islam that regards Mohammed's first true successor to be his son-in-law Ali.  Today, mostly associated with Iran.
  • simians
    Apes and monkeys.  Humans are simians.
  • socialism
    A system that emphasizes high governmental control over the economy, ideally on behalf of the lower classes.  Easily exploited by dictators for their personal gain, socialism is now often conflated with authoritarianism.
  • space-time
    The four-dimensional integration of space and time, used as a way to measure physical changes but also in recognition that space and time are bound together in relativity.
  • speciate
    To evolve into a new species after becoming isolated from sister populations, especially to the point of mating incompatibility.
  • spindle neuron
    A unique type of brain cell found only in great apes and a few other large-brained species.  It seems to be involved in higher thought functions such as self-awareness and social intelligence.
  • Spring of Nations
    The peak of revolutionary activity in 19th-century Europe, a wave from early 1848 to early 1849.
  • steppe
    A large area of flat unforested grassland, esp. in southeastern Europe or Siberia.
  • Sunda
    Southeast Asia, including the islands that were joined to the mainland in times of low sea levels.
  • Sunni
    The branch of Islam that regards Mohammed's first true successors to be his fathers-in-law Abu and Umar and his son-in-law Uthman.  Currently associated most strongly with Saudi Arabia.
  • supernova
    The explosion of a massive star.
  • symbiosis
    A mutually beneficial interaction between two different things, especially species.
  • synapsid
    Mammals and all extinct animals that are more closely related to mammals than to reptiles. Humans are synapsids.
  • taxon
    A category of living things, especially based on the Linnaean system of classification.
  • temperate
    Neither equatorial nor polar; moderate in climate.  Technically, the temperate zone ranges from latitudes of 23.5 degrees to 66.5 degrees in both the northern and southern hemispheres.
  • terrestrial
    On land.  Can be used as the opposite of aquatic or arboreal.
  • tetrapod
    A vertebrate with four limbs: amphibians, reptiles, birds, and mammals, including humans.
  • the Enlightenment
    The political / philosophical movement prevalent in Europe in the 18th century, raising questions about monarchy, state religion, and class relationships.
  • the Reformation
    The grassroots Christian movement, sparked by Martin Luther, challenging the monopoly of the Catholic Church on religious practice and interpretation.
  • theory of mind
    The ability to understand someone else's behavior as being driven by a mind like your own, but with a different perspective, interests, and needs.
  • Toumai
    The best-known specimen of a Sahelanthropus fossil, the only one discovered with a skull.
  • transistor
    The basic hardware unit of computer processing, a microscopic electric switch.
  • Triassic
    The earliest geological period of the Mesozoic (dinosaur) era, roughly 200 - 250 MYA.
  • TYA
    thousand years ago
  • TYO
    Thousand Years Old
  • Upper Paleolithic
    The archaeological period roughly 12 - 50 TYA, especially in Europe and western Asia, characterized by rapid innovation in stone tools and the spread of modern human behavior.
  • Vedas
    The foundational scriptures of Hinduism.  -2nd millennium, Sanskrit language, attributed to the Aryans.
  • vertebrate
    An animal with an internal skeleton.  Humans are vertebrates.
  • woodland
    Tree cover less dense than a forest, and predominantly at a single height.
  • xenophobia
    Fear, loathing, or distrust of "outsiders", however that may be defined in the subject's mind.
  • Y chromosome
    The chromosome that is passed from father to son and makes an organism male.
  • Yahweh
    aka Jehovah.  A god of ancient Israel.  His identity was merged with that of El (namesake of Isra-El) to form the persona of the first monotheistic God.
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