The   Urinary and Reproductive Cladogram depicts such a nested hierarchy of anatomical features of these animal systems.  All vertebrates posses the traits given at the node for the vertebrate ancestor (node 11).  All tetrapods possess the traits given at the node for the tetrapod ancestor (node 15).   All placental mammals possess the traits given at the node for the placental mammal ancestor (node 19).

     Apes consistently appear as a real, biological group—not a group of completely unrelated organisms which happen to share traits for no apparent reason.  Placental mammals are a real group.  Amniotes are a real group.  Deuterostomes are a real group, etc.  Biological groups are real—or at least there is an overwhelming amount of evidence that suggests that they are. 


1.        LUCA—Last common ancestor of all modern life on earth

2.        Ancestor of Protists, Plants, Fungi, and Animals

--meiosis and sexual reproduction

-- arginine-urea metabolic pathway (Prosser, 1973)

3.        Ancestor of Animals

Spermiogenesis although no acrosome (Harrison, Vol. 2)

Oocytes are large, 10x size oogonia (Harrison, Vol. 2)

4.        Ancestor of Animals with Tissues

--first gonads although not organs; may simply be aggregates of cells (Beklemishev vol. 2, Hickman, Hyman)

--ctenophores first ducts for gametes, although gametes released from mouth  (Beklemishev vol. 2, p. 393)

--sex cells migrate to gonads (Hyman, p. 431, Hickman)

5.        Ancestor Bilateran Animals

--the first excretory structures (although osmoregulation is primary function); absent in Acoela (Hickman)

--in advanced flatworms, compact ovaries and oviducts (Beklemishev vol. 2

--in some acoela, oocytes surrounded by folicular cells which nourish (Beklemishev vol. 2

6.        A nemertine-like ancestor of complex bilateran animals

--excretory tubules associated with blood vessels (Hickman)

7.        Coelomate Ancestor

--Metanephridia transport water, waste, gametes (Hickman 289)

--gonads lined by epithelium  (Hickman)

8.        Deuterostome Ancestor

--in hemicordates & urochordates oocytes are released from the ovary before meiosis is complete; meiosis is not completed development until fertilization  (Benito, form Harrison 1997, p. 93; Burighel, from Harrison, 1997, p. 282) 

9.        Chordate Ancestor

--podocytes(Benito, form Harrison 1997, p. 64 (Stach, 2000).. (Romer, p. 403)

--excretory structures in a segmental series (Romer, p. 403)

--in urochordates, follicular cells remain as a “corpus luteum” or follicular residuum after ovulation. (Burighel, from Harrison, 1997, p. 288) 

--in urochordates, intercellular bridges exist  between spermatocytes during spermatogenesis (Burighel, from Harrison, 1997, p. 295)

--9B Sertoli cells (Ruppert, from Harrison, 1997, p. 491).   

--9B spermatocytes progress towards lumen as meiosis occurs (Ruppert, from Harrison, 1997, p. 491).   

10.     Craniate Ancestor

--archinephritic duct unites series of excretory tubules (Romer, p. 404)

--archinephros releases waste to cloaca (Romer, p. 404)

--Bowman’s capsule (Hoar, 1969, Vol. I) 

--neck, and proximal segment I of tubule (Hoar, 1969, Vol. I). 

--urinary system can reabsorb filtered glucose and secrete ions (Hoar, 1969, Vol. I, p.  99). 

--pronephros (anterior excretory tubules which are functional only in adult hagfish; in vertebrates they degenerated during embryonic development) (Romer, p. 405)

--spermatogonia and oogonia produced in yolk sac rather than gonads (Romer, p. 421)

--gonads not segmented (Weichert, p. 280)

11.     Vertebrate Ancestor

--regulation of body osmolarity (in hagfish, body fluids similar ion concentrations as seawater) (Romer, p. 401)

--mesonephros and metanephros (together called the opistonephros) not segmented after embryonic development (Romer, p. 405)

-- collecting duct (Hoar, 1969, Vol. I). 

--increased efficiency of renal secretion and reabsorbion (Hoar, 1969, Vol. I, p.  99). 

--kidneys assume some of excretory function performed by hagfish liver (Hoar, 1969, Vol. I, p.  99). 

12.     Gnathostome Ancestor

--fenestrations in kidney glomeruli   (Hardisty 251)

--urea is the most abundant nitrogenous waste (Romer, p. 398 )

--renal corpuscle, proximal collecting tubule, distal collecting tubule (Romer, p. 398-400)

--increase in number of excretory tubules (Romer, p. 409)

--part of mesonephros used to transport sperm; sperm no longer released into coelom (Romer, p. 409)

--kidney is retroperitoneal (Weichert, 1970)

--a proximal segment II and a distal segment in renal tubule (Hoar, 1969, Vol. I). 

--bladder (in females only) (Romer, p. 416)

--kidneys able to excrete organic acids (Hoar, 1969, Vol. I, p.  99)

--most filtered water in urinary system is reabsorbed (Hoar, 1969, Vol. I, p.  99). 

--efferent ducts in males (Weichert, p. 319)

--oviduct (although ova still released into coelom) (Romer, p. 426)

--ciliated infundibulum to “catch” ova (Romer, p. 427)

--gonads paired (Kardong, p. 551)


13.     Bony Fish Ancestor

--JG cells (Hoar, 1969, Vol. I, p. 97).

--bladder in both males and females (Romer, p. 416)

-- intermediate segment of renal tubule (Hoar, 1969, Vol. I). 

14.     Sarcopterygian Fish Ancestor

15.     Tetrapod Ancestor

--archinephritic ducts are only used to transport sperm (Romer, p. 414)

--ductus defererns and an epididymis. (Weichert, p. 319)


16.     Amniote Ancestor

--renal corpuscle reduced in size to conserve water (Romer, p. 400)

--males no longer retain Muellerian ducts (as in some amphibians and lungfish) (Romer, p. 427)

--the metanephros is the primary kidney in adults (Kardong, p. 532)

--ovary joined to oviduct (Romer, p. 427)

--portions of oviduct specialize to become uterus and vagina (Romer, p. 429)

--(and cartilaginous fish) epididymis (Romer, p. 434)

--corpora cavernosa, glans penis, and clitoris (Romer, p. 441)

--corpora cavernosa becomes engorged with blood during sexual activity (Kardong, p. 562)

--oviducts develop from the Mullerian ducts rather than archinephric ducts (Weichert, p. 288)  

--Muellerian ducts do not persist in males (Weichert, p. 289).

--ova moved in oviducts through ciliary action and muscle contraction. (Weichert, p. 294

17.     Mammal Ancestor

--(and birds) loop of Henle in kidney (Romer, p. 400)

--mesonephros no loner functional after birth (Romer, p. 406)

--increase in the number of kidney tubules (Romer, p. 412)

--renal pelvis (Romer, p. 413)

--renal cortex and medulla (Romer, p. 413)

--kidney usually bean shaped (Romer, p. 413)

--loss of renal portal system (Romer, p. 414)

--ureters enter the bladder (rather than to the cloaca) (Kardong, p. 569)

--corpus luteum (Romer, p. 422)

--bulbourethral glands (Weichert, p. 322)

--cloaca begins to subdivide (Romer, p. 437)

--monotreme penis transitional between that of reptiles and higher mammals (Romer, p. 441)

--corpora spongiosum of penis (Kardong, p. 563)

--penis possesses glans and a foreskin. (Weichert, p. 327)

--the uterus produces nutrients for developing embryos (which is absorbed through the thin shells of monotremes); the embryos do develop inside the uterus to some degree.  (Weichert, p. 299).    

18.     Therian Mammal Ancestor (Marsupials and Placentals)

--modifications of oviduct (Romer, p. 431)

--testes descend into pelvis (Weichert, p. 310)

-- penis no longer in cloaca (Weichert, p. 327). 

--cloaca reduced (Kardong, p. 566)

--similar to eutherian estrus cycle with cyclical grwoth and loss of endometrium (Stonehouse, 1977)


19.     Placental Mammal Ancestor

mesonephros does not persist after birth

--prostate and seminal vesicles (Weichert, p. 322)

--ureters empty into the bladder more superiorly (as opposed to near base as in monotremes) (Weichert, 1970, p.269

--most placentals have a bipartite or bicornuate uterus rather than the primitive uterus duplex (w completely separate tubes) (Romer, p. 431)

--cloaca lost in most placentals but ventral portion retained in females as the vestibule (Romer, p. 439)

--testes descend into scrotum in most placentals (Romer, p. 441)

--testes are retained in the body cavity in monotremes, some insectivores, edentates, and elephants; a muscular pouch which is not a true scrotum exists in many rodents, some insectivores, and hyenas (Kardong, p. 559)

--single glans penis (forked in marsupials) (Kardong, p. 563)

20.     Primate Ancestor

-- the urinary and reproductive systems separate in females (Weichert, 1970, 270

—labia minora (Weichert, p. 301)

21.     Anthropoid Primate Ancestor (monkeys, apes, and humans)

--a reduction of penile spines (Stockey, 2002).  

22.     Catarrhine Primate Ancestor (Old World Monkeys, apes and humans)

--a reduction of penile spines (Stockey, 2002). 

23.     Ape Ancestor

--labia majora form part of vulva in humans and some apes (Weichert, p. 302)

--most apes have a menstrual cycle of about 30 days (gibbons 30; orangutans 31; gorillas 31; chimps 28-37, humans 28  )(Stockey, 2002).

--a reduction in the number of intromissions/copulation (usually multiple in OW) (Stockey, 2002)

24.     African Ape Ancestor

CH—scrotum located postpenially (Gibbs, 2002)

CH—increase in testis size (Gibbs, 2002)

Aftransverse rugae in vagina (Gibbs, 2002)

There is a gradual reduction of the baculum in higher apes from orangutans to gorillas to chimps to the absence of a baculum in humans.  In apes, three was a reduction in the number of intromissions/copulation (usually multiple in OW) (Stockey, 2002)


25.     Human Ancestor