Mammals {mammal} evolved from therapsids.
types
Mammals (Eutheria) are extinct multituberculates, monotremes like platypus, marsupials like kangaroo, and placental mammals (Placentalia).
evolution
Eutheria evolved from Theria. Early mammals included 30-gram Megazostrodon [-220000000] and Triconodon.
behavior
Early mammals hunted alone, signaled, and had territoriality. Voluntary muscles allowed rapid locomotion and good control.
body temperature
More food and oxygen allowed higher metabolic rate, more muscle action, and warm-bloodedness {homoiothermic, mammal}. Body temperature was higher than surroundings but lower than humans have now. Homeostasis allowed wider territory ranges and longer maturation times. Because early mammals were nocturnal, they only needed heating. Panting and sweating to cool body came later.
body temperature: hair
Mammals have hair, rather than scales, plates, or feathers, covering skin, to aid thermoregulation and insulation. They have sweat glands.
respiration
Diaphragm, bony palate, and turbinals allowed more oxygen and better respiration. Specialized red-blood-cell erythrocytes carry heme to provided better energy and oxygen management. Only warm-blooded animals can have erythrocytes.
reproduction
Reproductive-tract and digestive-tract openings became separate, allowing better and more reproduction and childcare varieties. Early mammals had birth rituals, courtship rituals, and sexual intercourse.
reproduction: mammaries
Sweat glands evolved into mammary glands, which provided balanced nutrition to young. Only warm-blooded animals can make milk. Milk redefined mother and father roles relative to children and allowed longer maturation and more brain growth. Mothers cared for babies until weaning.
teeth
Mammals have three teeth types: incisor, canine, and molar. They have two teeth sets, baby and adult, instead of continuous replacement, allowing head to be greater size in early life. Deciduous baby teeth and permanent adult teeth, rather than having continual replacement, allowed more teeth variety and more chewing. Head can be greater size in early life.
nervous system
Hippocampus and archicortex replaced some thalamus functions. Larger cerebellum allowed more sensorimotor coordination.
nervous system: involuntary muscle
Automatic circuits in ganglia and paleocortex control involuntary muscles, as in reptiles and birds. In lower mammals, archicortex and mesocortex or paleocortex add a supragranular layer to lower-animal granular and subgranular layers. In middle mammals, both supragranular and granular layers thicken, but subgranular layer stays the same.
nervous system: neocortex
In higher mammals, neocortex thickens, cellular complexity increases, newborn unmyelinated areas increase, and brain has more fissures. Paleocortex extension above ganglia forms neocortex to control voluntary muscles. All mammals have four lobes and three fissures in neocortex. Neocortex had four layers with minicolumns and interconnected specialized modules, to make maps for more complex local processing and more integration. Larger cerebrum allowed more spatial and temporal integration.
Higher mammals try alternate strategies to reach goals and identify object and event categories, such as individuals, selves, space, and time. Some mammals learn abstract symbols and categories. Some mammals generalize from specifics and specify objects from general categories. Some mammals learn relationships but cannot use analogies, metaphors, similes, parables, and mental models. Mammals have pleasant and unpleasant dreams. Mammals are curious, sentient, and know object categories, not just specific objects.
senses
Animals evolved new sensation abilities [Dawkins, 1987] [Griffin, 1974] [Griffin, 2001] [Griffin and Speck, 2004] [Haugeland, 1997].
senses: smell
Smell sense developed first, in amygdala and forebrain paleocortex.
senses: vision
At first, small eyes bulged out, as in tree shrews. Optic tectum allowed better object localization and size detection. Mammals typically have no or limited color vision, except for primates.
senses: hearing
Maleus evolved from cynodont articular jawbone, and incus evolved from cynodont quadrate jawbone, to work with stapes. Stapedius muscle controlled stiffness. Outer hair cells paralleled inner hair cells. These allowed hearing frequencies above 10000 Hertz and so high-frequency insect noises and baby cries. Outer hair cells can also change shape quickly, changing frequencies to which inner hair cells respond best. Early mammals had ear pinnae.
Mammals developed from juvenile therapsid cynodonts that matured quickly {pedomorphism}|.
People modified animals {domesticated animal}.
In Eurasia and north Africa, cow and ox came from auroch.
In west and central Asia, sheep came from Asiatic mouflon sheep.
In west Asia highlands, goat came from bezoar goat.
In Eurasia and north Africa, pig came from wild boar.
In south Russia, horse came from wild horses.
In Andes mountains, llama and alpaca came from guanaco.
In north Africa, donkey came from African wild ass.
In southeast Asia, bali cattle came from banteng, which relates to auroch.
In India and Burma, mithan came from gaur, which relates to auroch.
Arabian camel was in Arabia. Bactrian camel was in central Asia.
Reindeer were in north Eurasia. Water buffalo was in southeast Asia. Yak was in Himalayas and Tibet.
Primates live on ground or in small tree branches {fine-branch niche}|, like Australia and South America small nocturnal prosimians and arboreal marsupials.
Early placental mammals had long, sensitive snouts with large hairs {vibrissae} and good smell sense.
female quadruped {dam}.
flock or herd {drove}|.
Animals can have babies {pup, litter} each mating season {litter, pup}|.
Lions live in groups {pride}| with two or three males and five to ten females and cubs.
Mammals besides humans show paw preferences {handedness, mammal} but equally to left or right.
Mammal superior colliculus can integrate multiple senses {multisensory} at same spatial location, while other structures maintain distinct sensations for each sense [O'Regan and Noë, 2001].
Arginine vasopressin aids pair bonding {pair bonding, arginine vasopressin}.
Vocalization echoes give information. Dolphins and bats expanded this ability. Dolphins and bats use sonar {sonar, animal} to locate and categorize objects. They can project known signals into environment, receive reflected signals, and interpret altered signals. Signaling evolved from vocalization. Receiving evolved from auditory-brain sound processing, which locates and categorizes sounds.
Animals that are smart enough to suffer include horse, dog, apes, elephants, and dolphins, because they can do something about conditions that make them suffer {suffering, animal}.
Animal rhythms {biological rhythm}| depend on year, lunar month, tides, and day.
brain clock
Brain can time intervals {brain clock} using striato-cortical loops and frontal-cortex, caudate-putamen, and thalamus dopamine neurons. Clocks can be neuron circuits for each time interval, or neuron populations can code all intervals. Somatosensory lemniscal system can backdate events.
millisecond rhythm
Biochemical reactions have millisecond intervals. Coupled reaction systems can have cycles up to 100 seconds.
second rhythm
Heartbeat has ultradian rhythm regulated by pacemaker-neuron membrane-potential changes by voltage-sensitive K-channels.
minute rhythm
Cycles can repeat every few seconds or minutes for sessile, burrowing, and boring animals. Protein regulates cell 12-minute growth cycles. Inositol-trisphosphate receptor regulates calcium release in C. elegans in fifty-second intervals.
day rhythm
People can live on 23-hour and 25-hour cycles.
development rhythm
Reaction-cycle superpositions cause development cycles, which have intervals from minutes to hours to days.
month rhythm
Biological rhythms can be monthly, for hormones and temperature. Sex-hormone levels vary over lunar month. Marine organisms feed or rest with lunar tides. Shore-living invertebrates typically have tidal cycles and long-term rhythms related to Moon cycles.
year rhythm
Biological rhythms can be yearly, for migrations and moods. Yearly rhythms include hibernation and estivation. Breeding seasons typically are yearly. In autumn, plants can die or start low-metabolism state {dormancy, plant}.
In mammals, Mop3 gene product is main component of 24-hour biological clocks {biological clock}|, in hypothalamus, eye, testis, ovary, liver, heart, lung, and kidney, which work by positive and negative feedback among proteins. Mammals can rest themselves according to environment. Mutant Mop3 requires homozygosity. Clock-gene product acts as a pacemaker in hypothalamus suprachiasmatic nucleus (SCN), which synchronizes other organ clocks. CLOCK, PER, and MOP3 proteins have PAS domains. Circadian rhythm affects albumin D-element-binding protein {mDbp}, which does not regulate circadian rhythm.
Neuron networks {central pattern generator} control breathing, walking, and swimming.
Body has daily activity patterns {circadian rhythm}|. Internal mechanisms for daily cycles have 24-hour cycles.
functions
Body temperature, activity, blood pressure, blood pulse rate, blood volume, hormone levels, eosinophil levels, ACTH concentration, cortisol concentration, magnesium concentration, calcium concentration, 17-hydroxycorticosteroid concentration, sodium concentration, potassium concentration, catecholamine concentration, and phosphate concentration vary over day.
functions: time of day
Labor is most frequent and T lymphocytes are most at 1 AM. Growth hormone and deep sleep are greatest at 2 AM. Asthma attacks are most frequent at 4 AM. Body temperature is lowest at 4:30 AM. Menstruation starts most frequently at 6 AM. Insulin, blood pressure, heart rate, and cortisol are lowest at 6 AM, but melatonin is highest. Blood pressure starts to rise at 6:45 AM. Hay fever is worst at 7 AM. Melatonin production stops at 7:30 AM. Heart attack and stroke are most frequent at 8 AM. Rheumatoid arthritis is worst at 8 AM. T lymphocytes are fewest at 8 AM. Bowel movements are most likely at 8:30 AM. Alertness is highest at 10 AM. Blood hemoglobin concentration is highest at 12 PM. Coordination is best at 2:30 PM. Respiration is fastest, reflexes are quickest, and hand grip is strongest at 3 PM to 3:30 PM. Body temperature, heart rate, and blood pressure are highest at 4 PM. Muscle strength is greatest at 5 PM. Urination is most frequent at 6 PM. Blood pressure is highest at 6:30 PM. Body temperature is highest at 6:30 PM. Sensitivity to pain is greatest at 9 PM. Melatonin production starts at 9 PM, induces sleep at night, and maximizes just before morning. Bowel movements stop at 10:30 PM. Allergic reaction is most frequent at 11 PM.
cycle
Light affects retinal ganglion-cell melanopsin receptors, which catabolize PERIOD (PER) and TIMELESS (TIM) protein complexes in cytoplasm. Six hours later, catabolism is complete and CYCLE and CLOCK proteins bind. Then combined proteins bind to PER and TIM genes in cell nucleus, to start transcription. Six hours later, PER and TIM proteins bind in cytoplasm to form complex that blocks binding of CYCLE and CLOCK in cell nucleus.
After several days {jet lag}|, travelers can adjust to new local time. Travel across time zones can cause disturbances in sleep, digestion, and daily activity rhythms, and disturbances are unpleasant, impair performance, and last several days.
People have 90-minute to 100-minute cycles {ultradian rhythm}|. Desire to eat, desire for sex, sleep phases, daydreams, dreams, alertness, stomach contractions, and instinctual drives in general have ultradian rhythms. Infants have 60-minute movement and inactivity cycles.
Animals can have twilight activity {crepuscular}|.
Animals can have daytime activity {diurnal}|.
Animals can have nighttime activity {nocturnal}|.
Yearly rhythm is deep suspended animation, with low temperature, slow heartbeat, and slow breathing, for summer {estivation}|.
Yearly rhythm is deep suspended animation, with low temperature, slow heartbeat, and slow breathing, for winter {hibernation}|.
Main ancient mammals {Tribosphenida} had special-shape molar teeth {tribosphenic molar}.
Duck-billed platypus and spiny anteater {monotreme}| (Monotrema) are small. Monotremes evolved by pedomorphism from juvenile cynodonts that matured quickly. Monotremes lay eggs. Eggs hatch, and infants drink milk from mammary glands. Duck-billed platypus finds buried molluscs and insects by electric potentials.
Mammals {Theria} can have live births, rather than eggs laid outside body, and mammary glands. Eggs develop inside body. Babies emerge in fetal stage, requiring care of young during gestation and after birth. Parental care causes adult-behavior imitation. Theria developed from monotremes. Theria include Eutheria and marsupials.
Kangaroo, koala, wombat, wallaroo, and opossum {marsupial}| (Marsupia) {pouched mammal} have embryos that develop inside body and bear live young, at fetal stage, that crawl to pouch on abdomen outside, to drink milk from mammary glands and develop. Marsupials care for young. Theria developed from monotremes. Marsupials came from early Theria.
small, Australia, long snout, claws, termite eater {banded anteater}.
plant eater, Australia and New Guinea, large hind legs, long thick tail {kangaroo}.
Australia, arboreal, gray, furry ears, no tail {koala}.
nocturnal, arboreal, long tail {opossum} (Didelphis) (Didelphidae).
small, fur, Australia, arboreal, long prehensile tail {phalanger}.
Australia, aquatic, egg-laying, duck-like flexible bill, web feet, gray fur {platypus} (Ornithorhynchus anatinus).
small, carnivorous, black, long tail {Tasmanian devil}.
kangaroo-like but smaller {wallaby} (Macropodidae).
burrowing, plant eater, Australia, medium size, dense hair, short tail, flat snout {wombat}.
In Cretaceous, 150 million years ago to 100 million years ago, small, nocturnal insect-eaters {placental mammal}| (Placentalia) evolved.
anatomy: placenta
Tissue {placenta}, in which mother blood vessels commingle with embryo vessels, surrounds embryo inside uterus, allowing food and waste exchange. This allows more embryo growth, by improving nutrition and respiration.
anatomy: senses
First Eutheria had large ears and good hearing. They had vibrissae and good smell sense. They had small eyes, on head sides.
anatomy: nervous system
First Eutheria had larger brains than same-size reptiles.
biology: signal
Mammals other than primates have 10 to 40 different signals.
biology: children
All Eutheria have live birth. Eutheria have fewer births per mother, birth at later stage, and more care of young. Culture transmission requires relatively few young. Adults must outnumber young to preserve culture.
types
The 23 placental-mammal orders include bats, carnivores, cetacea, edentates, hooved, insectivores, primates, proboscids, rodents, scienia, and simple hooved. Carnivores include cat, dog, bear, and seal. Edentates include sloth, anteater, and armadillo. Insectivores include hedgehog, insectivore shrew, and mole. Primates include tree shrew, lemur, tarsier, and monkey. Lemurs and tarsiers are similar.
clades
Placental mammals have four clades. Clade I {Afrotheria} includes elephants, manatees, aardvarks, and elephant shrews. Clade II {Xenarthra} includes sloths, anteaters, and armadillos. Clade III {Euarchontoglires} {Supraprimates} includes rodents, primates, flying lemurs, and tree shrews. Clade IV {Laurasiatheria} includes cetaceans, bats, carnivores, hedgehogs, insectivore shrews, and moles.
clades: evolution
Afrotheria was first. Afrotheria and Xenarthra, clades I and II, split 103 to 105 million years ago, in Cretaceous, perhaps from South America and Africa separation.
Early superorder {Boreoeutheria}, of clades III Euarchontoglires and IV Laurasiatheria, split from Xenarthra 84 to 95 million years ago.
Euarchontoglires and Laurasiatheria {Epitheria} split 60 million years ago.
clades: I Afrotheria
Afrotheria is in Africa and includes golden mole (Chrysochloridae), otter shrew/tenrec, elephant shrew/sengi (Macroscelidea), aardvark (Tubulidentata), hyrax (Hyracoidea), mantee/dugong (Sirenia), and elephant (Proboscidea).
Tenrec (Tenrecidae) and otter shrew (Potamogalinae) have cloaca and can look like shrews, hedgehogs, mice, or otters. Golden mole lives in south Africa, eats insects, burrows, and looks like moles. Golden mole and otter shrew/tenrec are order (Afrosoricida).
Elephant shrew or jumping shrew (Macroscelididae) has long nose and looks like shrews.
Hyrax, mantee/dugong, and elephant are clade (Paenungulata). Hyrax lives in Africa and Middle East, looks like rabbit or guinea pig, and ferments food in cecum {copraphage}.
clades: II Xenarthra
Xenarthra developed in South America and includes armadillo (Cingulata), anteater (Vermilingua), and tree sloth (Folivora), which have strange joints {xenarthra}. Anteater includes silky anteater, giant anteater, and tamandua. Tree sloth includes two-toed and three-toed sloths. Anteater and tree sloth are group (Pilosa).
clades: III Euarchontoglires
Squirrel, mouse, and other rodents (Rodentia); rabbit, hare, and pika (Lagomorpha); treeshrew (Scandentia); coluga (Dermoptera); and primates are superorder (Euarchontoglires) (Supraprimates).
Coluga (Cynocephalidae) or cobego or flying lemur can glide from trees and lives in southeast Asia. Coluga, primate, and treeshrew are order (Euarchonta).
Pika (Ochotonidae), rock rabbit, or coney is like hamsters and squeaks {whistling hare}. Rodents and lagomorphs are order (Glires).
clades: IV Laurasiatheria
Laurasiatheria developed in Laurasia and are bats, hedgehogs, cetaceans, even-toed ungulates, odd-toed ungulates, carnivores, and scaly anteaters.
Hedgehogs (Erinaceinae) live in Eurasia and Africa. Gymnures or moonrats live in southeast Asia. Hedgehogs and gymnures are early order (Erinaceomorpha).
Shrews (Soricidae) include white-toothed shrews, red-toothed shrews, and African white-toothed shrews. Moles (Talpidae) include Talpinae, Scalopinae, and Uropsilinae. Solenodons (Solenodontidae) look like large shrews, are insectivores, and live in Cuba and Haiti. Moles, shrews, and solenodons (Soricomorpha) are order.
Artiodactyla order of even-toed ungulates includes pigs, hippopotamus, camels, giraffe, deer, antelope, cattle, sheep, and goats. Cetacea order includes whales, dolphins, and porpoises. Cetaceans probably evolved from hippopotamus (Whippomorpha) (Cetancodonta). Cetaceans and even-toed ungulates are order (Cetartiodactyla).
Even-toed and odd-toed ungulates are a group.
Order (Pegasoferae) is in Africa and south Asia and includes pangolins or scaly anteaters (Pholidota), carnivores (Carnivora), bats (Chiroptera), and odd-toed ungulates (Perissodactyla), such as horses. Carnivores and scaly anteaters are group (Ferae).
Mammals accept that individuals can have authority, resulting in different ranks {dominance hierarchy}|. Animals in groups have ranks or roles, relatively dominant or subordinate. Older males typically dominate.
authority
Different species use different authority symbols.
hierarchy
All societies have status hierarchies and/or resource controls.
change
Primates form alliances based on obligations and contact, to gain higher rank. Ranks are always shifting. Dominance fights are not deadly. Animals can try to act differently than rank. Others must catch and punish offenders. Animals can try to deceive, but only higher apes seem to try to make others' beliefs be wrong.
effects
Dominance hierarchy causes hostility to strangers, maintains peace in society, decreases new behaviors, and causes threats from younger males toward older males.
factors
Dominance behaviors increase at breeding times. Dominance behaviors increase at higher population densities.
Only humans laugh {laughter, human}, but other mammals appear happy.
Fat layer {blubber}| can protect body from cold.
Insectivores have hands with opposing thumb across from fingers {grasping hand}|, which allows better grip and more hand-eye coordination.
Some whales have oil {spermaceti}.
Proboscids have long trunk {trunk}| from nose.
Proboscids have elongated incisor teeth {tusk}|.
Insectivores have eyes facing front {forward vision}|, rather than on side, allowing better vision and eye-hand coordination and more space for brain frontal lobes.
Some echolocating bats, like horseshoe bat, scan for sound and then focus sound using nose structures {nose leaves}.
Cats have mirror-like layer {tapetum} behind retina to reflect light back through retina.
Individuals at rank must know to do some things and not do other things {deontic reasoning}.
Individuals in society attend to and remember rule breaking and act on previous-situation knowledge {indicative reasoning}.
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Date Modified: 2022.0225