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I’ll interpret your question to mean: What are the advantages for an animal to have a vertebral column?In a word: scaffolding to support against gravity. The difference between a hut and a high-rise is the differentiation between shelter and support elements. Invertebrates tend to have an equal or higher width-to-height ratio (crabs, insects, sponges, octopi, etc.) because the outer shelter (shell or hide) protects the soft innards. Result: A low center of gravity.In vertebrates, the bony internal scaffolding supports organs and offers attachment for muscles to gain traction for levering weight. Animals with a spine usually have a higher height-to-width ratio (vertical axis), which increases mobility efficiency in traveling transverse to gravity. Height off the ground (high center of gravity) combined with greater muscular strength allows launching and running which is essentially controlled bouncing against the ground to convert momentum and harmonics into motion most efficiently. The spine is a pretty good spring for loading/storing/releasing energy. Watch a cheetah at speed to see that spinal spring in action with its long continuation in a flexible tail for balance. No invertebrate and few vertebrates—except antelope, their prey—can come close to this exploitation of physics. https://www.reddit.com/r/gifs/comments/3gdcje/a_gif_from_earlier_thats_been_stabilized_very/.A shark’s vertebral column is cartilage, not bone, which allows its own specialized flexibility: http://jeb.biologists.org/content/219/18/2777.“Vertebral column, also called spinal column, spine, or backbone, in vertebrate animals, the flexible column extending from neck to tail, made of a series of bones, the vertebrae. The major function of the vertebral column is protection of the spinal cord; it also provides stiffening for the body and attachment for the pectoral and pelvic girdles and many muscles. In humans an additional function is to transmit body weight in walking and standing.” https://www.britannica.com/science/vertebral-column.Aye, there’s the rub (https://en.wikipedia.org/wiki/To_be,_or_not_to_be). There are also disadvantages to a vertebral column, starting with the fact that bone is anatomically expensive: it takes the right minerals in the diet as well as intensive vascular and muscular support. Controlling all this dynamic ability in turn requires an expensive nervous system, both central and peripheral. Most vertebrates have to be either active hunters or migrating herbivores to sustain the energy demands, including a highly developed nervous system for fast reflexes and ability to find food. Cold-blooded vertebrates like snakes and turtles can lower their metabolism to match the food supply but that means a tradeoff for dependence on the local climate for survival.Another disadvantage in vertebrates is that the spinal cord is fairly close to the surface of the skin. A single bite from a predator can prove crippling or fatal if it penetrates the spinal cord, whereas starfish and spiders can regrow a lost limb. All told, the fact remains that most animals (97%) are invertebrates: https://en.wikipedia.org/wiki/Invertebrate.Then for human vertebrates there’s an additional problem: mechanics. Four-footed animals distribute the weight and work of travel between fore- and hindquarters. Humans being bipedal, the spine itself has to bear the weight and, worse, the torque of the body above the hindquarters (hips), with only muscles and tendons linking support for all manner of bending, twisting and lifting motions. Spinal injuries and/or deterioration are the high price we humans pay for the advantage of having our hands free.But what an advantage! Arguably the single anatomic feature that accounts for our position atop the food chain is having hands free. (Other primates and a couple of other species like raccoons also have hands but most “hand time” is spent in locomotion.) Hands free allows for those famous opposable thumbs good for making and wielding tools, which creates a feedback loop requiring the nervous system to develop greater dexterity, producing in turn that oversize cerebral cortex which now discovers needs for new tools and machines extending our ability to work, travel, solve and create new problems, not least those of our own making.Bottom line: Vertebral spine > locomotion > brain means big advantages and disadvantages both.All depends on the job you’re trying to do.Thanks for the A2A.

Heck no.Of course, nothing is inevitable and we always can imagine alternative scenarios with an American victory without French participation.But it is hard to imagine a realistic one, given the facts of the time.It is very very difficult to envision a situation back then wherein the absence of French assistance and France’s active participation on the side of the Americans would have allowed an American rebel victory over Great Britain.Three factors won independence for the Americans. These were:1) American persistence2) French power (including “soft power” as well as “hard”), and3) British dissent.For a longer explanation of these, see my: Matthew Hogan's answer to Why did the British lose the American Revolution?The basic facts are that most of the sustained supplies of the Americans — everything from uniforms, to timely gunpowder and artillery — were French funded or arranged. Spain also supplied important materiel and even joined in the war against Great Britain, and inaugurated (with French support) assaults and threats against British bases/ports from Central America to the Eastern Meditterranean to the English Channel.But those efforts were also largely enabled by French diplomacy and support commitments towards Spain.France also nurtured more general European hostility to Britain, and in the Indian Ocean area and on or around Africa as well.French participation decided the timing of the successful outcome for the Americans.It was a regular navy French fleet and expeditionary force (regular army) that broke British rule in the 13 colonies of North America. This happened at Yorkown in late 1781 with the French army fighting alongside the American Continental Army and where the French naval units dealt with British naval units on their own, since there was no American navy with line-of-battle ships.The decision to do a coordinated strike at Yorktown was the idea of the French land commander to which Washington gave initially only grudging assent after prolonged resistance, preferring a more dangerous attack on New York.Meanwhile, the American local militia commander in Virginia was the French nobleman Lafayette, and the chief engineer for the decisive American artillery assault was the Frenchman duPortail (later a French Minister of War), both of whom were encouraged to join the Americans by the French government.—————French and British naval forces battle it out at the Virginia Capes, Sept. 1781. French blocking of sea access there ended any hope for the British at Yorktown.—————-The above does not even count the essential series of huge loans and grants by France to keep the American government and army in supply and salary over several years.It should also be noted that the timing of French entry into the war was essential as well.The Americans in late 1777 were snowed in at Valley Forge, the recent victory at Saratoga had only protected upper New York and New England. Philadelphia, the capital, had fallen as well as pretty much the whole mid-Atlantic region. The Congress was in exile and a team from London was coming to propose a deal for a peace. New York, meanwhile, had been retaken a year earlier. The British navy monopolized the waves and many inland waterways, minus the occasional American privateer nuisance and daring smuggler.Then, the war’s real revolution hit. France in early 1778 signed an alliance with the new “United States of North America” as it was called in the document.The reversal was astounding.Britain abandoned Philadelphia in a sudden evacuation from a town where almost minutes earlier they were all but partying, while playing an initially somewhat successful cat and mouse with the newly thawed out American troops.Thousands of British and auxiliary German-contractor troops were sent hustling by land in full headlong retreat to New York, which itself was said to be in the grip of mass panic as British forces throughout America braced themselves for a rival European superpower fleet to land on them in any moment.Other troops fled the mid-Atlantic by river and sea, at times throwing equipment into the waters like some parallel to the Fall of Saigon.A top level note from the First Lord of the Admiralty in London to the Commander in Chief in North America in early 1778 notified that the war on the American continent was strategically now “a secondary consideration” to the preservation of broader British possessions and waging counter activity to the French.The number of British troops in North America diminished by the thousands after 1777 (almost never to reach the same height inside America throughout the war) as they were pulled out to protect British possessions in the Caribbean or elsewhere.The allied might and participation (not just aid) from France would pin the British down, help directly crush their southern American forces, and finance the rebel army and new government to victory.Major supplies of money, materiel, intelligence, naval fleets, soldiers, and international diplomatic support for the Americans — alongside active great power inter-empire fighting — was the new rule of the day.It is hard to imagine a decisive American victory without the Franco-American alliance existing and bringing in big guns, big money, and big diplomacy to defeat the world’s premier empire and sea power.

Actually it’s when two side are similar, but one has a slight advantage. To press that advantage by assaulting in order to wear the enemy down, thus increasing one’s advantage at the cost of your own casualties.This was US Grant’s 1864 Campaign in a nutshell. He heavily engaged the Army of Northern Virginia in a series of bloody confrontations - Wilderness -Spotsylvania - Cold Harbor, etc. and sustained heavy casualties for his troubles. However, relative to the size of their respective armies, Lee’s army took heavier casualties, even if the raw numbers showed him with fewer losses.Grant could draw on more reserves, and Lee could not, forcing him to inexorably retreat to Richmond and Petersburg. That slight advantage spelled inevitable victory for the Union side and defeat for the Confederacy - and both commanders knew it.Brutal? Yes, quite. But sometimes it is necessary. When you think of it, the Central Pacific Campaign under Nimitz was much the same. MacArthur’s South Pacific was better conducted (bypassing Rabaul and other strong points) but there were still places we had to assault directly in order to proceed.