A Nested Hierarchy

     The Circulatory Cladogram depicts  a nested hierarchy of anatomical features of animal circulatory systems.  All vertebrates possess 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).

     You can make a hypothetical family tree based on traits of the circulatory system.  If evolution has not occurred, it is not only unexpected that you could devise such a tree, it is certainly unexpected that such a tree coincides with family trees designed based on the traits of the nervous system.  Or the skeletal system.  Or the muscular system.  Or embryological development.  Or the fossil record.  Or molecular evidence.  But they do coincide.  Life on earth does not give the impression of having appeared from nowhere without common ancestors—the groups of living things are a series of branches from a great, ancient family tree.

     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

--iron porphyrins (a group of molecules to which heme belongs) (Hoar, 1983)

--globin (Hausladen, 2001)

--Rh family of genes which often function in ammonium transport (Okuda, 2002)

--carbonic anhydrase (Hoar, 1983)

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

--evolution of aerobic respiration which requires oxygen

--Rh gene family (Huang, 2001)

3.        Ancestor of Animals

--wandering amoeba-like phagocytes to for defense against microbes (Hoar, 1983)

--lectins (Gamulin, 1994; Schacke, 1994a)

--immunoglobulin domain and immunoglobulin-like molecules (Schacke, 1994; Schacke, 1994a)

--desmosomes, actin, microtubules  (Grell, from Harrison, Vol.2)

--ameobocytes with many inclusions, some of which are phagosomes (Harrison, Vol. 2)47

4.        Metazoan Ancestor


5.        Bilateran Ancestor

6.        Higher Bilateran Ancestor

--blood vessels (Hickman)

--contractile muscle surrounding blood vessels (which primitively pumped blood in the absence of a heart) (Hickman)

--minor blood vessels branching from major ones (Hickman)

--corpuscles and amebocytes in blood (Hickman)

--pigments in blood?—some nemertines have hemoglobin but others can have no pigment or one of several other pigments (Hickman)

--endothelial lining in blood vessels (Dutta, 365) 

--fenstrated basilar layer of endothelial lining (Dutta, 366)

--cells similar to macrophages and liver endothelial cells (Seternes, 2002).


7.        Ancestor of Coelomates

--directional blood flow; in nemertines blood can flow both directions through blood vessels (Hickman)

--fibrinogen-like lectins (Xu and Doolittle, 1990)

--genetic mechanisms of heart formation shared by protostomes and deuterostomes: homologus homeodomain genes are involved in the earliest formation of the heart (Msh-2 in Drosophila and csx in mammals) (Komuro, 1993);  tinman/csk is expressed in heart progenitor cells in protostomes and deuterostomes (Gerhart, 2000); in flies, Dpp functions with wingless in the formation of the heart tube  while their vertebrate counterparts (bone morphogenetic proteins and Wnt/Wg respectively),   function in the formation of vertebrate embryonic hearts (Nakamura, 2003).

8.        Ancestor of Deuterostomes

--blood vessels to pharyngeal slits   (Harris; (Benito, form Harrison 1997, p. 59)

-- striated muscle in heart  (Benito, form Harrison 1997, p. 44)

--amoebocyte blood cells typically possess kidney-shaped nuclei. (Benito, form Harrison 1997, p. 61)

-- the heart is surrounded by a pericardium formed by a blind sac of the coelom which doesn’t completely separate the heart from the coelom  (Benito, form Harrison 1997, p. 20; Hickman). 

9.        Chordate Ancestor

--(urochordates, 9A) blood vessels to pharyngeal slits more extensive; perform gas exchange  (Harris)

-- most pigments in tunicates are in the hemocytes which occur in blood vessels or in connective tissue spaces. (Burighel, from Harrison, 1997). 

--macrophages, different kinds of granular amoebocytes with odd-shaped nuclei which perform phagocytosis (Burighel, from Harrison, 1997, p. 269)

--heart muscle cells require calcium for their contraction and are joined by tight junctions and gap junctions. (Webster, 1974, p. 48-9; Burighel, from Harrison, 1997).

--natural killer cell receptors (Khalturin, 2003).    

--reactions against transplantation of foreign tissue using macrophages and morula cells (which possess some features of lymphocytes (Khalturin, 2003; Rinkevich, 1998)

--complement genes and 2 interleukin receptor genes which probably function in innate immunity(Dehal, 2002)..

--opsonins, agglutinins, lectins, cytokines, and hemolysins. (Burighel, from Harrison, 1997, p. 269).  

--(cephalochordates, 9B) branchial artery homologous to vertebrate truncus arteriosus (Willey, 47)

--(cephalochordates, 9B) aortic arches (Willey, 49)

--(cephalochordates, 9B) aortic arches carry oxygenated blood to the dorsal aorta (Willey, 49)

--(cephalochordates, 9B) subintestal vein carries blood from gastrointestinal tract to liver where portal system is formed (from the embryonic subintestinal vein in craniates the hepatic portal vein forms) (Willey, 54)

--(cephalochordates, 9B) Amphioxus has capillaries, valves in veins and arteries; vessels have the same structure as vertebrates (Dutta, 367)

--(cephalochordates, 9B) Endostylar artery in Amphioxus is homologue of abdominal aorta (Dutta 367)


10.     Craniate Ancestor

--alkaline phosphatase found in neutrophils (Hine, 1990).

--reduction in the number of aortic arches (Romer)

--a heart with separate chambers: the  sinus venosus, a single atrium, and a single ventricle (Torrey) 

--the sinus venosus is the site where the contraction of the heart in initiated, (which is also true of the embryonic hearts of all vertebrates) (Torrey).

--In lampreys and hagfish, the circulatory system is almost a closed one, but a system of venous sinuses and plexuses are reminiscent of the open circulatory system of many invertebrates (Hardisty, p. 242)

--heart is composed of cardiac muscle (Kardong, p. 462)

--variable cardiac output (Forster, 1997)

--catecholamines, ANP, and neuropeptides to regulate circulatory physiology; catecholamines stimulate moderate increases in the contraction rate (Forster, 1997). 

-- valves permit only one direction of flow between heart chambers; sinoatrial, atrioventricular, and semilunar heart valves.  (Kardong, p. 462). 

--epicardium and an endocardium (Webster, 1974, p. 129)

--thin walled vessels of vascular plexuses in both lampreys and hagfish may be primitive lymphatic vessels; most agree that there are no true lymphatic vessels in lampreys.   (Hardisty, 249)

--increase in blood vessels to skeletal muscle over condition in Amphioxus (Willey)

--reduction in number of aortic arches (Kardong)

--cells homologous to thymus (Romer 448)

--“spleen” represented by diffuse tissue associated with the G.I. tract (Torrey, 1979).

--external and internal carotid arteries; internal carotids servicing brain (2)

--celiac, anterior mesenteric, posterior mesenteric, renal, and gonadal arteries (2)

--first blood cells form in yolk sac and are nucleated (even in mammals) (2)

--heterodimeric immunoglobulins (similar to both antibodies and T cell receptors in hagfish) secreted into plasma in immune response (Varner, 1991).


11.     Vertebrate Ancestor

--ability of hemoglobin to transport carbon dioxide; Haldane effect (Hoar, 1983)

--neutrophils are typically the most common white blood cell; basophils the least common (Torrey). 

--cartilage surrounding the pericardial cavity Hardisty (242) 

--skeletal and cardiac muscle (including desmosomes and intercalated disks in cardiac muscle) is similar to that of higher vertebrates (Hardisty 242).

--artery walls in lampreys contain smooth muscle and collagen; the walls of the aorta also contain elastic fibers.  (The walls of veins are thinner with less smooth muscle, Hardisty, 248). 

--Hematopoeisis occurs in pronephros and in primitive bone marrow of cartilaginous provertebral arches (Hardisty 251).

--unpaired arteries from the dorsal aorta to the gastrointestinal tract, including the celiac (Hardisty 250)

--thymus (Romer 448)

--intercalated disks and desmosomes (Hardisty). 

--truncus arteriosus (Hardisty; (Kardong)). 

--heart valves are present (Kardong)

 -- In larval lampreys, the pericardial cavity is connected to the coelomic cavity (as in hagfish) but the two cavities are separated in adulthood (Weichert, 1970).

 (Guenther, 151).

--the heart forms from the anterior part of the subintestinal vein during embryonic development, and the subintestinal vein forms originally from a fused pair of vitelline veins.  (Hardisty 242-5)

--atrioventricular and semilunar valves (Kardong, p. 463).

--The sinus venosus collects blood from the cardinal veins, jugular vein, and the hepatic vein (Kardong)

--vagal input to heart; heart responds to ACh (Prosser, 1973)

--the sinus venosus receives this nervous input (although the sinus venosus fuses with the right atrium in higher amniotes (Torrey).

--chordae tendinae attach to the atrioventricular valve. (Weichert, 1970).    

--chromaffin-like cells are present in the hearts of lampreys and higher vertebrates including mammals. (Webster, 1974, p. 127).

--reduction in blood volume, venous sinuses, venous propulsors, and increase in  blood pressure over the condition in hagfish (Forster, 1997

--reduction in number of aortic arches (Kardong)

--regulation of heart by Dorsal motor nucleus of vagus (Porges, 1988)

--celiac artery (Hardisty)

--greater development of branchial “thymus” (Shintani, 1999; Weichert, 1970)

--lymphocytes (or cells indistinguishable from them in lampreys) (Mayer, 2002).   

--Spi gene function in lymphocyte maturation (Shintani, 1999)


12.     Gnathostome Ancestor (vertebrates with jaws)

--two rounds of gene duplication which create myoglobin and hemoglobin genes from ancestral globin gene followed by α and β genes from the ancestral hemoglobin

--increase in the efficiency of carbonic anhydrase (Tufts, 2003)

--coronary blood vessels (in lampreys, blood can pass between cardiac muscle fibers) (Kardong 460; Hardisty 242)

--vagus nerve and neurotransmitter ACh inhibit the heart (in lampreys, both stimulate the heart) (Hardisty 251)

--reduction in the number of aortic arches (to 6) (Romer)

--hematopoeisis in embryonic kidney (through to reptiles and birds) and adult kidney (through reptiles) (Romer 448-9)

--venous valves. (Webster, 1974, p. 67; Hoar, 1983).

-- catecholamines increase both heart rate and contractibility (Hoar, 1970)

--spleen (Romer 452)

--renal portal veins (through birds) (Romer 474-5)

--posterior portion of posterior cardinal veins interrupted Romer 474

--lateral abdominal veins (which mammals retain only as umbilical veins) Romer 477

--external and internal carotid arteries (Kardong)

--hepatic portal vein no longer contractile (Guenter 154)

--faster transmission of impulses between atria and ventricles (Webster, 1974, p. 54)

--increase in blood vessels to skeletal muscle over condition in lamprey (Hardisty)

--more elastic fibers in ventral aorta in sharks (Prosser, 1973)

--subclavian and iliac vessels to fins

--loss of accessory hearts—contractile portions of blood vessels other than the branchial heart in Amphioxus and hagfish (Kardong)

--innervation of heart (no nerves innervate heart in hagfish) Kardong

--muscarinic cholinergic receptors and the heartrate decreases with ACh. (Prosser, 1973)

--reduction of sinuses between vessels leads to a reduction in blood volume (Webster, 1974, p. 57; Forster, 2001))

--reduction in number of aortic arches (Kardong)

--thymus (Hoar, 1983)

--different antibody classes, including IgM (1 V, 2 D, 1 J, 1 C) and are not reshuffled (Hohman, 1993, ). 

--antibodies possess  V, D,  J,  and C regions (Hohman, 1993, ). 


13.     Bony Fish Ancestor

--eosinophil peroxidase (weak or absent in cartilaginous fish) (Hine, 1990).

--lymphatic vessels, lined by endothelium (Dutta, 371)

--hematopoesis in liver (through to amphibians and turtles) (Romer 450)

--both the gill vessels of fish and lung vessels of amphibians are constricted by Ach and dilated by E.; in fish and mammals E dilates coronary arteries and constricts most systemic  (Prosser, p. 831)

--GATA family of transcription factors important in mammalian hematopoeisis (perhaps from an earlier point)(Lyons, 2002).

--lymphatic vessels (although more primitive fish possessed thin-walled sinuses which empty into the veins (Dehal, 2002; Torrey, 1979; Romer). 

--cells homologous to natural killer cells (Harris, 1991)

--natural killer cell receptors are encoded in a leukocyte receptor cluster region (Yoder, 2001; Sato, 2003).

B and T cells

--regulation of heart by Spinal sympathetic nervous system (Porges, 1988)


14.     Sarcopterygian Fish Ancestor

--signficant Haldane effect (Hoar, 1983)

--partial interatrial septa (although a partial interventricular septum may be present, it may not be homologous with that of amniotes) (Kardong 465)

--sinus venosus empties into right atrium, pulmonary vein into left (Kardong p. 465).

--pulomary vein from lungs to left atrium

--posterior vena cava (Romer 475)

--the pulmonary artery develops as a branch of aortic arch VI which also services gills before emptying into the dorsal aorta through the ductus arteriosus (amphibians have the same) (Kardong)

--increased amount of cardiac muscle in atria and ventricles (Webster, 1974)


15.     Amphibian Ancestor

--completely separate right and left atria

--subclavian veins empty into anterior vena cavae (Romer 478)

--the aortic arches are reorganized and the common carotid forms from the ventral aorta which formerly connected aortic arches III and IV;  the internal carotid, together with aortic arch III and part of the dorsal aorta, joins it and the carotid body forms at the terminus of the common carotid (Kardong, Romer)

--further development of limb vessels: axillary, brachial, radial, ulnar, femoral, saphenous, popliteal, tibial blood vessels

-- lymph “hearts” with skeletal muscle and valves (Romer 479)

--first two aortic arches disappear early in development (5)

-- tissue homologous to pharyngeal tonsils (Weichert, 1970)247


16.     Amniote Ancestor

--several biochemical traits of red blood cells; occasional loss of nuclei from red blood cells (Mauro, 1997)

--hematopoeisis in adult limited to red bone marrow and spleen (Torrey)

--a completely separate pulmonary circuit; no ductus arteriosus connecting pulmonary and systemic circuits in adult (Kardong)

--sinus venosus smaller but still contains SA node. 

--a pulmonary trunk and at least one systemic aortic trunk leave the heart (Kadong 467)

--partial division of ventricles (Kardong 467)

--posterior cardinal veins of embryo remain in adults only as azygos veins (Romer 475)

--reduction of renal portal system (Romer 475)

--lymphatic cisterns or lymphatic sites at same sites as true lymph nodes in mammals and some water birds (Kardong, 484)

--hearts create higher pressure, greater cardiac output, and separate oxygenated from deoxygenated blood. (Kardong 467).

--sinus venosus reduced  (Kardong 467)

--Conduction system of heart in amniotes; (in more primitive vertebrates, muscles contracted in a wave (Romer, 482)

-- conus arteriosus present in embryo only; makes up portions of vessels leaving the Heart (Romer 488)

--amniotes increase the number of veins innervated (Prosser, p. 831)

--regulation of heart by Adrenal medulla (Porges, 1988)

--pharyngeal tonsils. (Weichert, 1970)247


17.     Mammal Ancestor

--the red bone marrow is the site of red blood cell and granulocyte synthesis while sites such as the thymus and spleen are important for the maturation and proliferation of agranulocytes (Torrey).    

--platelets (Jiang, 2003).  

--interventricular septum creates right and left ventricles

--an AV node in heart (Kardong, 461)

--bone marrow more important in hematopoeisis (birds as well) (Romer 450)

--some lymphocyte proliferation (lymph nodes) & production (thymus) occurs outside bone marrow (Romer 450)

--complex coiled masses of vessels called rete mirable; occur in many mammalian tails, perhaps as heat-saving device; humans still have the coccygeal glomus in their tail (Romer 455)

--valves (present in primitive lymph “hearts”) in lymphatic vessels (also in birds) (Romer 458)

--loss of lateral head veins;  internal jugular veins replace them (Romer 472-3)

--loss of renal portal system (Romer 475)

--iliac veins empty into the posterior vena cava (as opposed to the lateral abdominal veins or renal portal veins)

--loss of carotid duct connecting carotid artery to dorsal aorta which is retained in some amphibians and reptiles (Romer)

--true lymph nodes (Kardong, 484)

--an increase in number of lymph nodes (Torrey, 1979).  

--anucleate red blood cells (3)

-- the right branch  of the fourth aortic arch degenerates (its only remnant being the base of the right subclavian artery) and the left branch of the fourth aortic arch composes the aorta (Torrey, 1979)

--palantine and lingual tonsils only in mammals (Weichert, 1970)247

--thymus forms from the ventral portions of pouches 3 and 4 instead of dorsal portions  (Weichert, 1970)245-6

--regulation of heart by Vagal pathways from nucleus ambiguous (Porges, 1988)


18.     Therian Mammal Ancestor (Marsupials and Placentals)

--spleen more compact (Romer 452)

--although the embryonic external carotid artery is small and the stapedial artery is large, as in the condition in non-therian adult vertebrates, the external carotid grows into the branches of the stapedial artery which is subsequently reduced or absent (Romer 468)

--umbilical arteries

--umbilical vein; empties into both the liver and the hepatic vein

--foramen ovale diverts most blood from lungs during fetal development


19.     Placental Mammal Ancestor

--additional duplications of β globin genes

--sinus venosus only present as SA node after embryonic development (Kardong, 475)

--in many mammals, including humans, left common cardinal vein disappears (473)

--embryonic lateral abdominal veins become umbilical veins (Romer 477)

--in many mammals, left common cardinal vein degenerates in embryonic development; there is only one resultant anterior/superior vena cava (Romer)

--ductus arteriosus is functional in embryo but becomes the ligamentum arteriosum in adults. (Kardong 479)


20.     Primate Ancestor

--eta hemoglobin gene mutates to become a pseudogene


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

--ABO blood groups (some prosimians have B-like antigens); M blood antigen (3)


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

--blood returns from the brain through the internal jugular as opposed to the external jugular and vertebral veins typical of other mammals. (not strep primates more prim pattern) (Kimbel, 1984)


23.     Ape Ancestor

  --N blood antigen


24.     African Ape Ancestor

--low frequencies of several alternate channels including occipital-marginal,  (Falk, 1986; Falk, 1983)

—cephalic vein limited to forearm in at least some specimens (Gibbs, 2002)

palmar metacarpal artery may be included in origin of radialis indicus (Gibbs, 2002)

—radial artery enters palm at dorsum of first interosseous space (Gibbs, 2002)

—superior ulnar clooateral artery sometimes originates from brachial artery (Gibbs, 2002)

—lateral thoraci artery usually is an independent branch of axillary artery (Gibbs, 2002)


24B. Human-Chimp clade

interosseous artery arises from common interosseous artery (Gibbs, 2002)

—superficial palmar artery passes over thenar muscles (Gibbs, 2002)

dorsalis pollicis (Gibbs, 2002)

—medial femoral circumflex sometimes originates from profunda femoris (Gibbs, 2002)

—hamstrings receive musclualr branches of profunda femoris artery (Gibbs, 2002)


25.     Human Ancestor

--A. africanus and H. habilis retain the transverse-sigmoid sinus drainage system most common in apes, including humans.  A. afarensis and boisei have enlarged occipital-marginal sinuses (Kimbel, 1984).

--Occipial-marginal sinus systems do occur in modern populations and in Pleistocene Homo (Kimbel, 1984)

--O/M drainage in A. afarensis may have been linked to upright posture (Falk, 1986; Falk, 1983).