Study traces AIDS virus origin to 100 years ago

“Researchers took advantage of the fact that HIV mutates rapidly. So two strains from a common ancestor quickly become less and less alike in their genetic material over time. That allows scientists to "run the clock backward" by calculating how long it would take for various strains to become as different as they are observed to be. That would indicate when they both sprang from their most recent common ancestor.

The new work used genetic data from the two old HIV samples plus more than 100 modern samples to create a family tree going back to these samples' last common ancestor. Researchers got various answers under various approaches for when that ancestor virus appeared, but the 1884-to-1924 bracket is probably the most reliable, Worobey said.”

Study traces AIDS virus origin to 100 years ago

cynodonts

Mammaliamorpha

Mammaliaformes

Mammalia: All descendants fromthe MRCA of living mammals.

cynodonts

Mammaliamorpha

Mammaliaformes

cynodonts

Mammaliaformes (formation of dentary-squamosal“single jaw hinge” complete)

cynodonts

Mammaliamorpha (transition todentary-squamosal joint begins)

Trait Pelycosaurs Therapsids CynodontsPosture: sprawling intermediateupright

Teeth: weakly heterodont increasingly heterodontstrongly hetero

Palate: no secondary palate partialcomplete

“-apsidy” small temporal fenestra enlarged fenestravastly expanded

Postdentary bones: present, large present, reducedabsent

greatly reduced

Mammaliaformes (formation of dentary-squamosal“single jaw hinge” complete)


cynodonts

Mammaliamorpha (transition todentary-squamosal joint begins)

Mammaliamorpha

Mammaliaformes

Mammalia

Morganucodon

•Completion of dentary-squamosal jaw joint•Cheekteeth divided into premolars and molars•Diphyodonty

•BUT TINY! For 170 million years!

Pa

leo

zoic

Me

sozo

icMammalia (and some mammaliaforms)

Mammaliamorpha

Mammaliaformes


cynodonts

Mammaliamorpha

Mammaliaformes

Mammalia

Multituberculates (extinct prototherians)


Late Jurassic-Mid. Miocene (ca. 150 m.y.)



Diverse, found on all continents




Ever-growing lower incisors,plagialacoid (blade-like)molariform teeth




Ever-growing lower incisors,plagialacoid (blade-like)molariform teeth

Outcompeted to extinction? (rodents, early primates...)

Mammaliamorpha

Mammaliaformes

Mammalia (CLASS)

Met

ath

eria

Met

ath

eria

Eu

ther

iaE

uth

eria

Theria(SUBCLASS)

ProtoPrototheria (SUBCLASS)theria (SUBCLASS)

(INFRACLASSES)(INFRACLASSES)

Extant mammalian diversity

1 Order (Monotremata)2 Families3 species

Infraclass Metatheria

Infraclass Eutheria

7 Orders19 Families272 species

18 Orders114 Families4354 species

Subclass Prototheria Subclass Theria

Class MAMMALIA

Extant mammalian diversity

1 Order (Monotremata)2 Families3 5 species

Infraclass Metatheria

Infraclass Eutheria

7 Orders19 21 Families272 331 species

18 21 Orders114 130 Families4354 5078 species

Subclass Prototheria Subclass Theria

Class MAMMALIA

xxxxxx

xxxxx

xxxx

The radiation of placental mammals

Since end of Mesozoic, placental (eutherian) mammals dominant terrestrial vertebrates on all continents except Australia and Antarctica.

When and why did this diversification occur?

“Age of Mammals”

“Age of Dinosaurs”

K/T boundaryK/T boundary

Tert

iary

K/TK/Tboundaryboundary

Most/all eutherian orders originated & diversifyAFTER K/T

(traditionally, fossils supported this)



Orders originate BEFORE K/T but don’t diversify untilAFTER K/T

(more recently discovered fossils support)



Orders originate BEFORE K/T but don’t diversify untilAFTER K/T

(more recently discovered fossils support)

Most orders originate & diversify BEFORE K/T(older molecular studies support)

1 Order (Monotremata) 2 Families

Tachyglossidae (echidnas or “spiny anteaters”)4 species.

Ornithorhynchidae (platypus)1 species

Subclass Prototheria

Few fossils, never very diverse. BUT PERSISTED.



Echidnas: fossils from 55-60 Mya, oldest in S. AMERICA




Platypus: fossils from 120 Mya, oldest in AUSTRALIA(Paleocene fossils in S. AMERICA).




Platypus: fossils from 120 Mya, oldest in AUSTRALIA(Paleocene fossils in S. AMERICA).

Many plesiomorphic features, but some apomorphies.


SKULL FEATURES:

•No teeth in living adults BUT fossil platys & living neonates have, then lose. LOSS=apomorphy


SKULL FEATURES:

•No teeth in living adults BUT fossil platys & living neonates have, then lose. LOSS=apomorphy•No lacrimals (APOMORPHY)


SKULL FEATURES:

•No teeth in living adults BUT fossil platys & living neonates have, then lose. LOSS=apomorphy•No lacrimals (APOMORPHY)•Cranial sutures fused, indistinct (APOMORPHY)


SKULL FEATURES:

•No teeth in living adults BUT fossil platys & living neonates have, then lose. LOSS=apomorphy•No lacrimals (APOMORPHY)•Cranial sutures fused, indistinct (APOMORPHY)•Jugal reduced or absent (APOMORPHY)


SKELETAL FEATURES:


SKELETAL FEATURES:•Epipubic bones present, large (PLESIOMORPHY)


SKELETAL FEATURES:•Epipubic bones present, large (PLESIOMORPHY)•Cervical ribs (PLESIOMORPHY)


SKELETAL FEATURES:•Epipubic bones present, large (PLESIOMORPHY)•Cervical ribs (PLESIOMORPHY)•Horny, hollow spur on inside of ankle (APOMORPHY)


Warren et al. (2008). Nature 453, 175-183.

SKELETAL FEATURES:•Epipubic bones present, large (PLESIOMORPHY)•Cervical ribs (PLESIOMORPHY)•Horny, hollow spur on inside of ankle (APOMORPHY)•Pectoral girdle with large precoracoids, coracoids, interclavicle (PLESIOMORPHY)


SKELETAL FEATURES:•Epipubic bones present, large (PLESIOMORPHY)•Cervical ribs (PLESIOMORPHY)•Horny, hollow spur on inside of ankle (APOMORPHY)•Pectoral girdle with large precoracoids, coracoids, interclavicle (PLESIOMORPHY)•Skeleton sprawling, “reptilian” (PLESIOMORPHY) BUT, good for swimming, digging.


OTHER FEATURES:•Pouch (echidnas only)


OTHER FEATURES:•Pouch (echidnas only)•Testes permanently abdominal (no scrotum)


OTHER FEATURES:•Pouch (echidnas only)•Testes permanently abdominal (no scrotum)•Uteri fused


OTHER FEATURES:•Pouch (echidnas only)•Testes permanently abdominal (no scrotum)•Uteri fused•Leathery egg with nutrient-rich yolk


OTHER FEATURES:•Pouch (echidnas only)•Testes permanently abdominal (no scrotum)•Uteri fused•Leathery egg with nutrient-rich yolk•Rostrum lacks vibrissae, elongate•cloaca (but....)


OTHER FEATURES:•Pouch (echidnas only)•Testes permanently abdominal (no scrotum)•Uteri fused•Leathery egg with nutrient-rich yolk•Rostrum lacks vibrissae, elongate•cloaca (but...)•Endothermic, but low Tb and metabolic rates


OTHER FEATURES:•Pouch (echidnas only)•Testes permanently abdominal (no scrotum)•Uteri fused•Leathery egg with nutrient-rich yolk•Rostrum lacks vibrissae, elongate•cloaca (but...)•Endothermic, but low Tb and metabolic rates•Electroreception (snout), including echidnas


Study traces AIDS virus origin to 100 years ago

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